Trapping atoms on a transparent permanent-magnet atom chip

We describe experiments on trapping of atoms in microscopic magneto-optical traps on an optically transparent permanent-magnet atom chip. The chip is made of magnetically hard ferrite-garnet material deposited on a dielectric substrate. The confining magnetic fields are produced by miniature magnetized patterns recorded in the film by magneto-optical techniques. We trap Rb atoms on these structures by applying three crossed pairs of counter-propagating laser beams in the conventional magneto-optical trapping (MOT) geometry. We demonstrate the flexibility of the concept in creation and in-situ modification of the trapping geometries through several experiments.Comment: Modifications: A) Reference I. Barb et al., Eur. Phys. JD, 35, 75 (2005) added. B)Sentence rewritten: We routinely capture more than 10^6 atoms in a micro-MOT on a magnetized pattern. C) The magnetic field strengths are now given in Teslas. D) The second sentence in the fourth paragraph has been rewritten in order to more clearly describe the geometry and purpose of the compensation coils.E) In the seventh paragraph we have rewritten the sentence about the creation of the external magnetic field for the magnetic-domain patterning. F) In the ninth paragraph, we clarify the way to shift the trap center. G) Caption of Fig. 4 changed. H) We have modified paragraph 12 to improve the description on the guiding of the trap center along a toroidal pattern. I) The last two sentences of the manuscript have been rewritte

Jacobi-Nijenhuis algebroids and their modular classes

Jacobi-Nijenhuis algebroids are defined as a natural generalization of Poisson-Nijenhuis algebroids, in the case where there exists a Nijenhuis operator on a Jacobi algebroid which is compatible with it. We study modular classes of Jacobi and Jacobi-Nijenhuis algebroids

Hubbard Models as Fusion Products of Free Fermions

A class of recently introduced su(n) `free-fermion' models has recently been used to construct generalized Hubbard models. I derive an algebra defining the `free-fermion' models and give new classes of solutions. I then introduce a conjugation matrix and give a new and simple proof of the corresponding decorated Yang-Baxter equation. This provides the algebraic tools required to couple in an integrable way two copies of free-fermion models. Complete integrability of the resulting Hubbard-like models is shown by exhibiting their L and R matrices. Local symmetries of the models are discussed. The diagonalization of the free-fermion models is carried out using the algebraic Bethe Ansatz.Comment: 14 pages, LaTeX. Minor modification

Interplane magnetic coupling effects in the multilattice compound Y_2Ba_4Cu_7O_{15}

We investigate the interplane magnetic coupling of the multilattice compound Y_2Ba_4Cu_7O_{15} by means of a bilayer Hubbard model with inequivalent planes. We evaluate the spin response, effective interaction and the intra- and interplane spin-spin relaxation times within the fluctuation exchange approximation. We show that strong in-plane antiferromagnetic fluctuations are responsible for a magnetic coupling between the planes, which in turns leads to a tendency of the fluctuation in the two planes to equalize. This equalization effect grows whit increasing in-plane antiferromagnetic fluctuations, i. e., with decreasing temperature and decreasing doping, while it is completely absent when the in-layer correlation length becomes of the order of one lattice spacing. Our results provide a good qualitative description of NMR and NQR experiments in Y_2Ba_4Cu_7O_{15}.Comment: Final version, to appear. in Phys. Rev. B (Rapid Communications), sched. Jan. 9

Clinical implications of cephalic vein morphometry in routine cardiac implantable electronic device insertion

Background: Morphometric parameters of the venous vasculature constitute an important aspect in successful cardiac implantable electronic device (CIED) insertion. The purpose of this study was to present morpho-anatomical variations of the cephalic vein (CV) and their effect on the course of CIED implantation procedures, based on the patients from our centre. Materials and methods: We analysed contrast venography results obtained during first-time lead placement. Venography was indicated in the cases of problematic lead introduction with either the CV cutdown or axillary/subclavian vein puncture techniques. The 214 cases of venography (15%) performed out of 1425 first-time lead placement in the period 2011–2013 were divided into 9 subgroups according to the most commonly observed CV variations of similar morpho-anatomical features that limited the use of the CV cutdown technique for lead insertion. Results: The following CV morphometric parameters were found to be unfavo­urable in terms of lead placement: CV diameter of ≤ 1 mm (18%), sharp curva­ture of the terminal CV segment as it joined the axillary vein (14%), terminal CV bifurcation (9%), additional CV branches (7%) or tributaries (7%), stenoses (5%), sharply winding course (5%), single CV with a supraclavicular course (4%). Conclusions: The radiographic records obtained during the procedures allowed us to assess the prevalence of those atypical CV variations in our study group, with graphic presentation of characteristic types and sporadically reported CV variations

A variational principle for volume-preserving dynamics

We provide a variational description of any Liouville (i.e. volume preserving) autonomous vector fields on a smooth manifold. This is obtained via a ``maximal degree'' variational principle; critical sections for this are integral manifolds for the Liouville vector field. We work in coordinates and provide explicit formulae

Limited-are a modelling of stratocumulus over South-Eastern Pacific

This paper presents application of the Weather Research and Forecasting (WRF) model to limited-area modeling of atmospheric processes over the subtropical south-eastern Pacific, with the emphasis on the stratocumulus-topped boundary layer. The simulations cover a domain from the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) field project conducted in the subtropical south-eastern Pacific in October and November 2008. We focus on a day where the UK's BAe-146 research aircraft encountered Pockets of Open Cells (POCs) at the very western edge of its flight track, rather than on the entire campaign as investigated in previous limited-area modeling studies. Model results are compared to aircraft observations with the main conclusion that the simulated stratocumulus-topped boundary layer is significantly too shallow. This appears to be a combination of an already too shallow boundary layer in the dataset used to provide initial and lateral boundary conditions, and the inability of the WRF model to increase the boundary-layer height. Several sensitivity simulations, applying different subgrid-scale parameterizations available in the model, a larger computational domain and longer simulations, as well as a different dataset providing initial and lateral boundary conditions were all tried to improve the simulation. These changes appeared to have a rather small effect on the results. The model does simulate the formation of mesoscale cloud-free regions that one might consider similar to Pockets of Open Cells observed in nature. However, formation of these regions does not seem to be related to drizzle-induced transition from open- to closed-cell circulations as simulated by LES models. Instead, the cloud-free regions appear to result from mesoscale variations of the lower-tropspheric vertical velocity. Areas of negative vertical velocity with minima (a few cm s<sup>−1</sup>) near the boundary layer top seem to induce direct evaporation of the cloud layer. It remains to be seen in LES studies whether the mechanism seen in the model is realistic or if it is simply an artifact of interactions between resolved and parameterized processes

Selected clinical challenges of a supraclavicular cephalic vein in cardiac implantable electronic device implantation

Background: Supraclavicular variations of the cephalic vein (CV) are detected sporadically. A somewhat more common finding is a CV variation with the typical course of the main vessel but with an additional supraclavicular branch, called the jugulocephalic vein (JCV). The aim of the study was to detect supraclavicular CVs or JCVs via intra-operative venography as well as assess their effects on primary and later revision cardiac implantable electronic device (CIED) procedures in our patients. Materials and methods: We analysed venographic images obtained during CIED procedures at our centre between 2011 and 2015. Out of the 324 venographies conducted during first-time CIED implantation, we identified 14 showing either a supraclavicular course of the CV itself or a persistent JCV. Among revision procedure venographies, we identified 1 case of pertinent CV variations. These vessels had been morphometrically altered by previous medical interventions. Results: Based on topography and morphometric parameters, we identified three anatomical variations of supraclavicular vessels: 2 cases of a supraclavicular CV and 12 cases of an infraclavicular CV accompanied by a persistent supraclavicular JCV (with the diameter larger than that of the main CV in 5 cases and smaller in 7 cases). In 2 cases the enlarged diameter of the JCV was probably due to increased collateral venous flow resulting from thrombotic lesions in the subclavian vein. Conclusions: Supraclavicular CV variations are rare. Nonetheless, they may significantly affect both first-time and later revision CIED procedures. The presence of a supraclavicular vein is an indication for diagnostic venography in the area of the clavipectoral triangle before the CIED procedure

Characterizing the Mechanical Stiffness of Passive-Dynamic Ankle-Foot Orthosis Struts

People with lower limb impairment can participate in activities such as running with the use of a passive-dynamic ankle-foot orthosis (PD-AFO). Specifically, the Intrepid Dynamic Exoskeletal Orthosis (IDEO) is a PD-AFO design that includes a carbon-fiber strut, which attaches posteriorly to a custom-fabricated tibial cuff and foot plate and acts in parallel with the impaired biological ankle joint to control sagittal and mediolateral motion, while allowing elastic energy storage and return during the stance phase of running. The strut stiffness affects the extent to which the orthosis keeps the impaired biological ankle in a neutral position by controling sagittal and mediolateral motion. The struts are currently manufactured to a thickness that corresponds with one of five stiffness categories (1 = least stiff, 5 = most stiff) and are prescribed to patients based on their body mass and activity level. However, the stiffness values of IDEO carbon-fiber struts have not been systematically determined, and these values can inform dynamic function and biomimetic PD-AFO prescription and design. The PD-AFO strut primarily deflects in the anterior direction (ankle dorsiflexion), and resists deflection in the posterior direction (ankle plantarflexion) during the stance phase of running. Thus, we constructed a custom apparatus and measured strut stiffness for 0.18 radians (10°) of anterior deflection and 0.09 radians (5°) of posterior deflection. We measured the applied moment and strut deflection to compute angular stiffness, the quotient of moment and angle. The strut moment-angle curves for anterior and posterior deflection were well characterized by a linear relationship. The strut stiffness values for categories 1–5 at 0.18 radians (10°) of anterior deflection were 0.73–1.74 kN·m/rad and at 0.09 radians (5°) of posterior deflection were 0.86–2.73 kN·m/rad. Since a PD-AFO strut acts in parallel with the impaired biological ankle, the strut and impaired biological ankle angular stiffness sum to equal total stiffness. Thus, strut stiffness directly affects total ankle joint stiffness, which in turn affects ankle motion and energy storage and return during running. Future research is planned to better understand how use of a running-specific PD-AFO with different strut stiffness affects the biomechanics and metabolic costs of running in people with lower limb impairment