Gyrofluid simulations of collisionless reconnection in the presence of diamagnetic effects

The effects of the ion Larmor radius on magnetic reconnection are investigated by means of numerical simulations, with a Hamiltonian gyrofluid model. In the linear regime, it is found that ion diamagnetic effects decrease the growth rate of the dominant mode. Increasing ion temperature tends to make the magnetic islands propagate in the ion diamagnetic drift direction. In the nonlinear regime, diamagnetic effects reduce the final width of the island. Unlike the electron density, the guiding center density does not tend to distribute along separatrices and at high ion temperature, the electrostatic potential exhibits the superposition of a small scale structure, related to the electron density, and a large scale structure, related to the ion guiding-center density

Gyrofluid simulations of collisionless reconnection in the presence of diamagnetic effects

The effects of the ion Larmor radius on magnetic reconnection are investigated by means of numerical simulations, with a Hamiltonian gyrofluid model. In the linear regime, it is found that ion diamagnetic effects decrease the growth rate of the dominant mode. Increasing ion temperature tends to make the magnetic islands propagate in the ion diamagnetic drift direction. In the nonlinear regime, diamagnetic effects reduce the final width of the island. Unlike the electron density, the guiding center density does not tend to distribute along separatrices and at high ion temperature, the electrostatic potential exhibits the superposition of a small scale structure, related to the electron density, and a large scale structure, related to the ion guiding-center density

Gyrofluid simulations of collisionless reconnection in the presence of diamagnetic effects

The effects of the ion Larmor radius on magnetic reconnection are investigated by means of numerical simulations, with a Hamiltonian gyrofluid model. In the linear regime, it is found that ion diamagnetic effects decrease the growth rate of the dominant mode. Increasing ion temperature tends to make the magnetic islands propagate in the ion diamagnetic drift direction. In the nonlinear regime, diamagnetic effects reduce the final width of the island. Unlike the electron density, the guiding center density does not tend to distribute along separatrices and at high ion temperature, the electrostatic potential exhibits the superposition of a small scale structure, related to the electron density, and a large scale structure, related to the ion guiding-center density

Mode signature and stability for a Hamiltonian model of electron temperature gradient turbulence

Stability properties and mode signature for equilibria of a model of electron temperature gradient (ETG) driven turbulence are investigated by Hamiltonian techniques. After deriving the infinite families of Casimir invariants, associated with the noncanonical Poisson bracket of the model, a sufficient condition for stability is obtained by means of the Energy-Casimir method. Mode signature is then investigated for linear motions about homogeneous equilibria. Depending on the sign of the equilibrium "translated" pressure gradient, stable equilibria can either be energy stable, i.e.\ possess definite linearized perturbation energy (Hamiltonian), or spectrally stable with the existence of negative energy modes (NEMs). The ETG instability is then shown to arise through a Kre\u{\i}n-type bifurcation, due to the merging of a positive and a negative energy mode, corresponding to two modified drift waves admitted by the system. The Hamiltonian of the linearized system is then explicitly transformed into normal form, which unambiguously defines mode signature. In particular, the fast mode turns out to always be a positive energy mode (PEM), whereas the energy of the slow mode can have either positive or negative sign

Mediastinitis and sternal prosthesis infection successfully treated by minimally invasive omental flap transposition

Purulent mediastinitis is a possible serious complication after mediastinal surgery. We report the case of a localized sternal plasmocytoma treated by sternectomy and prosthetic repair, who needed a second surgery for a fistulizing mediastinitis. Five months earlier, in another Hospital, the patient underwent sternal resection and reconstruction with a “sandwich” prosthesis (Methyl-methacrylate and Marlex mesh). Suppurative mediastinitis occurred and septic shock resolution was observed after the spontaneous opening of a mediastinal cutaneous fistula. After referring to our Unit the patient underwent extensive local and systemic preparation and nutritional support; the infected prosthesis was then removed and the gap filled by a laparoscopically-prepared omental flap. Adequate preoperative management, removal of any infected material and minimally invasive omental flap transposition allowed the successful treatment of this life-threatening condition

Use of lead isotopic ratios as geographical tracer for Lambrusco PDO wines

In this study, the lead isotope signature was tested with the aim to verify its potential as geographic tracer for wine production and particularly for the Lambrusco PDO wines of the province of Modena (Italy). A solid phase extraction procedure, for separating lead from the investigated matrices, soil and wine, was optimized. Furthermore, different mathematical models, based on an exponential law and internal or external correction approach, were evaluated for the correction of instrumental mass dependent fractionation. The optimized analytical procedure yielded isotopic ratio data relative to the lead NIST 981 standard, 208Pb/206Pb = 2.16664 and 207Pb/206Pb = 0.914645, in good agreement both with the tabulated values and with the most recent literature data. Measured isotope ratio data highlight the contribute of multiple lead sources in bottled wine but different from the one present in soils

A novel technique for measurement of orthodontic mini-implant stability using the Osstell ISQ device

© 2019 by The EH Angle Education and Research Foundation, Inc. Objectives: To develop and validate a method for application of the Osstell ISQ device in the assessment of mini-implant stability. Materials and Methods: An adaptor was developed for attachment of Osstell\u27s SmartPeg onto a variety of orthodontic mini-implants. For validation of the adaptor, Benefit mini-implants were inserted into bone blocks that mimicked different stability conditions. The Osstell device was used to assess mini-implant stability with the adaptor (test measurement) and conventional SmartPeg attachment (gold-standard measurement). Implant stability quotient (ISQ) values were assessed for agreement, repeatability, and reproducibility. Results: Strong positive correlations were found between ISQ values obtained using the novel adaptor and the conventional attachment. Repeatability and reproducibility of ISQ values with the adaptor were similar to those obtained with the conventional attachment. Conclusions: A method was developed and validated to assess the stability of orthodontic mini-implants using the Osstell system. The novel mini-implant adaptor provided repeatable and reproducible measurements of mini-implant stability, which agreed with those obtained using a conventional SmartPeg attachment. This adaptor permits noninvasive stability assessment of various designs of mini-implants, most of which are incompatible with the conventional SmartPeg attachment