711 research outputs found

    From nonassociativity to solutions of the KP hierarchy

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    A recently observed relation between 'weakly nonassociative' algebras A (for which the associator (A,A^2,A) vanishes) and the KP hierarchy (with dependent variable in the middle nucleus A' of A) is recalled. For any such algebra there is a nonassociative hierarchy of ODEs, the solutions of which determine solutions of the KP hierarchy. In a special case, and with A' a matrix algebra, this becomes a matrix Riccati hierarchy which is easily solved. The matrix solution then leads to solutions of the scalar KP hierarchy. We discuss some classes of solutions obtained in this way.Comment: 7 pages, 4 figures, International Colloquium 'Integrable Systems and Quantum Symmetries', Prague, 15-17 June 200

    Fabrication of low-cost, large-area prototype Si(Li) detectors for the GAPS experiment

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    A Si(Li) detector fabrication procedure has been developed with the aim of satisfying the unique requirements of the GAPS (General Antiparticle Spectrometer) experiment. Si(Li) detectors are particularly well-suited to the GAPS detection scheme, in which several planes of detectors act as the target to slow and capture an incoming antiparticle into an exotic atom, as well as the spectrometer and tracker to measure the resulting decay X-rays and annihilation products. These detectors must provide the absorption depth, energy resolution, tracking efficiency, and active area necessary for this technique, all within the significant temperature, power, and cost constraints of an Antarctic long-duration balloon flight. We report here on the fabrication and performance of prototype 2"-diameter, 1-1.25 mm-thick, single-strip Si(Li) detectors that provide the necessary X-ray energy resolution of ∟\sim4 keV for a cost per unit area that is far below that of previously-acquired commercial detectors. This fabrication procedure is currently being optimized for the 4"-diameter, 2.5 mm-thick, multi-strip geometry that will be used for the GAPS flight detectors.Comment: Accepted for publication at Nuclear Instrumentation and Methods A, 12 pages, 11 figure

    A dimension-breaking phenomenon for water waves with weak surface tension

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    It is well known that the water-wave problem with weak surface tension has small-amplitude line solitary-wave solutions which to leading order are described by the nonlinear Schr\"odinger equation. The present paper contains an existence theory for three-dimensional periodically modulated solitary-wave solutions which have a solitary-wave profile in the direction of propagation and are periodic in the transverse direction; they emanate from the line solitary waves in a dimension-breaking bifurcation. In addition, it is shown that the line solitary waves are linearly unstable to long-wavelength transverse perturbations. The key to these results is a formulation of the water wave problem as an evolutionary system in which the transverse horizontal variable plays the role of time, a careful study of the purely imaginary spectrum of the operator obtained by linearising the evolutionary system at a line solitary wave, and an application of an infinite-dimensional version of the classical Lyapunov centre theorem.Comment: The final publication is available at Springer via http://dx.doi.org/10.1007/s00205-015-0941-

    Transient psychosis due to painless thyroiditis in a patient with anxiety disorder: a case report

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    <p>Abstract</p> <p>Introduction</p> <p>There are few reports on thyrotoxic psychosis caused by diseases other than Graves' disease or toxic nodular goiter.</p> <p>Case presentation</p> <p>A 64-year-old Japanese woman was treated for anxiety disorder in our clinic for 10 years. She had five episodes of transient psychosis during the first five years. When she developed psychosis without neck pain 10 years after her first visit, a laboratory reexamination revealed that she had subclinical hyperthyroidism, and tested positive for antithyroid autoantibodies, negative for thyroid stimulating hormone receptor antibody and had decreased radioactive iodine uptake. She was diagnosed as having painless thyroiditis. The hyperthyroidism disappeared within a month, and the psychosis lasted for three months.</p> <p>Conclusion</p> <p>To the best of our knowledge, this is the first report of psychosis due to painless thyroiditis-induced hyperthyroidism. Physical symptoms of painless thyroiditis are often so mild that careful differential diagnosis is necessary in the cases of transient psychosis.</p

    A Criterion for Photoionization of Pregalactic Clouds Exposed to Diffuse Ultraviolet Background Radiation

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    To elucidate the permeation of cosmic ultraviolet (UV) background radiation into a pregalactic cloud and subsequent ionization, the frequency-dependent radiative transfer equation is solved, coupled with the ionization process. A spherical top-hat cloud which is composed of pure hydrogen is assumed. As a result, it is shown that the self-shielding, although it is often disregarded in cosmological hydrodynamic simulations, could start to emerge shortly after the maximum expansion stages of density fluctuations. The present analysis reveals that the Stro"mgren approximation leads to overestimation of the photoionization effects. Also, the self-shielded neutral core is no longer sharply separated from surrounding ionized regions; a low but noticeable degree of ionization is caused by high energy photons even in the self-shielded core. The present results may be substantial on considering the biasing by photoionization against low-mass galaxy formation.Comment: 12 pages, Latex, 3 figures, To appear in ApJ, July 20, 1998 issue, email: [email protected]

    Toward oral delivery of biopharmaceuticals: an assessment of the gastrointestinal stability of 17 peptide drugs

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    A major barrier to successful oral delivery of peptide and protein molecules is their inherent instability in the lumen of the gastrointestinal tract. The aim of this study was to determine the stability of 17 disparate peptide drugs (insulin, calcitonin, glucagon, secretin, somatostatin, desmopressin, oxytocin, [Arg(8)]-vasopressin, octreotide, ciclosporin, leuprolide, nafarelin, buserelin, histrelin, [d-Ser](4)-gonadorelin, deslorelin, and goserelin) in gastric and small intestinal fluids from both humans and pigs, and in simulated gastric and intestinal fluids. In human gastric fluid, the larger peptides including somatostatin, calcitonin, secretin, glucagon, and insulin were metabolized rapidly, while the smaller peptides showed good stability. In human small intestinal fluid, however, both small and large peptides degraded rapidly with the exception of the cyclic peptide ciclosporin and the disulfide-bridge containing peptides octreotide and desmopressin, which showed good stability. The stability of peptides in both simulated gastric fluid and pig gastric fluid correlated well with stability in human gastric fluid. However, it was not possible to establish such a correlation with the small intestinal fluids because of the rapid rate of peptide degradation. This work has identified the molecular features in the structure of a wide range of peptides that influence their stability in the environment of the gastrointestinal tract, which in turn will allow for better selection of peptide candidates for oral delivery

    Soliton locking phenomenon over finite magnetic field region in the monoaxial chiral magnet CrNb3S6

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    Previous magnetic measurements for the chiral magnet CrNb3S6 have shown that the soliton penetration and soliton dissipation in the chiral soliton lattice state strongly depend on the crystal\u27s size and shape. We performed magnetic measurements for a thin single crystal of CrNb3S6 with a thickness 3 μm, permitting the existence of approximately 60 solitons, and observed the magnetization (M)—magnetic field (H) curve with a remarkable full M–H loop. By investigating the minor loop of the M–H curve in detail, we found that the inside of the full M–H loop allows an infinite number of quasi-stable states for each eigen number of solitons, utilizing a non-negligible distribution of the thickness around 3 μm. This study reveals that in a microcrystal with a chiral axis length of a few micrometers, any magnetic state with an arbitrary soliton number can be created in a certain H range within the full M–H loop
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