2,352 research outputs found

    A SPIRED\texttt{SPIRED} code for the reconstruction of spin distribution

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    In Nuclear Magnetic Resonance (NMR), it is of crucial importance to have an accurate knowledge of the sample probability distribution corresponding to inhomogeneities of the magnetic fields. An accurate identification of the sample distribution requires a set of experimental data that is sufficiently rich to extract all fundamental information. These data depend strongly on the control fields (and their number) used experimentally. In this work, we present and analyze a greedy reconstruction algorithm, and provide the corresponding SPIRED\texttt{SPIRED} code, for the computation of a set of control functions allowing the generation of data that are appropriate for the accurate reconstruction of a sample distribution. In particular, the focus is on NMR and the Bloch system with inhomogeneities in the magnetic fields in all spatial directions. Numerical examples illustrate this general study.Comment: 31 pages, 6 figure

    Rational Ligand Design for the Arylation of Hindered Primary Amines Guided by Reaction Progress Kinetic Analysis

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    We report the Pd-catalyzed arylation of very hindered α,α,α-trisubstituted primary amines. Kinetics-based mechanistic analysis and rational design have led to the development of two biarylphosphine ligands that allow the transformation to proceed with excellent efficiency. The process was effective in coupling a wide range of functionalized aryl and heteroaryl halides under mild conditions.National Institutes of Health (U.S.) (GM5816)Fundación Obra Social de La Caixa (Predoctorate Fellowship

    Adjustable microchip ring trap for cold atoms and molecules

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    We describe the design and function of a circular magnetic waveguide produced from wires on a microchip for atom interferometry using deBroglie waves. The guide is a two-dimensional magnetic minimum for trapping weak-field seeking states of atoms or molecules with a magnetic dipole moment. The design consists of seven circular wires sharing a common radius. We describe the design, the time-dependent currents of the wires and show that it is possible to form a circular waveguide with adjustable height and gradient while minimizing perturbation resulting from leads or wire crossings. This maximal area geometry is suited for rotation sensing with atom interferometry via the Sagnac effect using either cold atoms, molecules and Bose-condensed systems

    Absence of a consistent classical equation of motion for a mass-renormalized point charge

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    The restrictions of analyticity, relativistic (Born) rigidity, and negligible O(a) terms involved in the evaluation of the self electromagnetic force on an extended charged sphere of radius "a" are explicitly revealed and taken into account in order to obtain a classical equation of motion of the extended charge that is both causal and conserves momentum-energy. Because the power-series expansion used in the evaluation of the self force becomes invalid during transition time intervals immediately following the application and termination of an otherwise analytic externally applied force, transition forces must be included during these transition time intervals to remove the noncausal pre-acceleration and pre-deceleration from the solutions to the equation of motion without the transition forces. For the extended charged sphere, the transition forces can be chosen to maintain conservation of momentum-energy in the causal solutions to the equation of motion within the restrictions of relativistic rigidity and negligible O(a) terms under which the equation of motion is derived. However, it is shown that renormalization of the electrostatic mass to a finite value as the radius of the charge approaches zero introduces a violation of momentum-energy conservation into the causal solutions to the equation of motion of the point charge if the magnitude of the external force becomes too large. That is, the causal classical equation of motion of a point charge with renormalized mass experiences a high acceleration catastrophe.Comment: 13 pages, No figure

    Laparoscopic reinforced sleeve gastrectomy: early results and complications

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    BACKGROUND: Sleeve gastrectomy (SG) was pioneered as a two-stage intervention for super and super-super obesity to minimize morbidity and mortality; it is employed increasingly as a primary procedure. Early outcomes and integrity of laparoscopic SG (LSG) against leak using a technique incorporating gastric transection-line reinforcement were studied. METHODS: Between 2003 and 2009, 121 patients underwent LSG (16, two-stage; 105, primary). Of the patients, 66% were women, mean age 38.8 ± 10.9 (15.0-64.0), and body mass index (BMI, kg/m(2)) 48.7 ± 9.3 (33.7-74.8). Bovine pericardium (Peri-Strips Dry [PSD]) was used to reinforce the staple line. Parametric and nonparametric tests were used, as appropriate. The paired t test was used to assess change from baseline; bivariate analyses and logistic regression were used to identify preoperative patient characteristics predictive of suboptimal weight loss. RESULTS: Mean operative time was 105 min (95-180), and mean hospitalization was 5.6 days (1-14). There was no mortality. There were 6 (5.0%) complications: 1 intraoperative leak, 1 stricture, 1 trocar-site bleed, 1 renal failure, and 2 wound infections. There were no postoperative staple-line leaks. Following 15 concomitant hiatal hernia operations, 3 (20%) recurred: 1 revised to RYGB and 2 in standby. Two post-LSG hiatal hernias of the two-stage series required revisions because of symptoms. BMI decreased 24.7% at 6 months (n = 55) to 37.5 ± 9.3 (22.2-58.1); %EWL was 48.1 ± 19.3 (15.5-98.9). Twelve-month BMI (n = 41) was 38.4 ± 10.5 (19.3-62.3); %EWL was 51.7 ± 25.0 (8.9-123.3). Forty-eight-month BMI (n = 13) was 35.6 ± 6.8 (24.9-47.5); %EWL was 61.1 ± 12.2 (43.9-82.1) (p 70% of patients who experienced <50% EWL at 6 months. At 2 weeks, 100% of type 2 diabetes patients (n = 23) were off medication (mean HbA(1C), 5.9 ± 0.5%; glycemia, 90.0 ± 19.9 mg/dL (p < 0.01) at 3 months). CONCLUSIONS: Laparoscopic PSD-reinforced LSG as a staged or definitive procedure is safe and effective in the short term and provides rapid type 2 diabetes mellitus reduction with a very low rate of complications

    Cervicothoracic Intradural Arachnoid Cyst Misdiagnosed as Motor Neuron Disease

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    Recognizing syndromes which mimic ALS is crucial both to avoid giving this diagnosis erroneously and since there may be appropriate treatments. We report a 63-year-old woman diagnosed with possible ALS five years ago based on upper and lower motor neuron signs with typical electrophysiology and normal cranial MRI. At reassessment, spinal MRI revealed a cervicothoracic cyst with cord compression that was successfully treated neurosurgically. Histopathology confirmed an arachnoid origin as suspected from MRI. Spinal cysts may mimic ALS and need to be thoroughly excluded by appropriate imaging

    Thiol groups of normal immunoglobulin G

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    Influence of topography on tide propagation and amplification in semi-enclosed basins

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    An idealized model for tide propagation and amplification in semi-enclosed rectangular basins is presented, accounting for depth differences by a combination of longitudinal and lateral topographic steps. The basin geometry is formed by several adjacent compartments of identical width, each having either a uniform depth or two depths separated by a transverse topographic step. The problem is forced by an incoming Kelvin wave at the open end, while allowing waves to radiate outward. The solution in each compartment is written as the superposition of (semi)-analytical wave solutions in an infinite channel, individually satisfying the depth-averaged linear shallow water equations on the f plane, including bottom friction. A collocation technique is employed to satisfy continuity of elevation and flux across the longitudinal topographic steps between the compartments. The model results show that the tidal wave in shallow parts displays slower propagation, enhanced dissipation and amplified amplitudes. This reveals a resonance mechanism, occurring when\ud the length of the shallow end is roughly an odd multiple of the quarter Kelvin wavelength. Alternatively, for sufficiently wide basins, also Poincaré waves may become resonant. A transverse step implies different wavelengths of the incoming and reflected Kelvin wave, leading to increased amplitudes in shallow regions and a shift of amphidromic points in the direction of the deeper part. Including the shallow parts near the basin’s closed end (thus capturing the Kelvin resonance mechanism) is essential to reproduce semi-diurnal and diurnal\ud tide observations in the Gulf of California, the Adriatic Sea and the Persian Gulf
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