Surface impedance measurements on Nb3_{3}Sn at high magnetic fields

Nb$_{3}$Sn is a superconductor of great relevance for perspective RF applications. We present for the first time surface impedance $Z_s$ measurements at 15 GHz and low RF field amplitude on Nb$_{3}$Sn in high magnetic fields up to 12 T, with the aim of increasing the knowledge of Nb$_{3}$Sn behavior in such conditions. $Z_s$ is a fundamental material parameter that directly gives useful information about the dissipative and reactive phenomena when the superconductor is subjected to high-frequency excitations. Therefore, we present an analysis of the measured $Z_s$ with the aim of extracting interesting data about pinning in Nb$_{3}$Sn at high frequencies. From $Z_s$ we extract the vortex motion complex resistivity to obtain the $r$-parameter and the depinning frequency $\nu_p$ in high magnetic fields. The comparison of the results with the literature shows that the measured $\nu_p$ on bulk Nb$_{3}$Sn is several times greater than that of pure Nb. This demonstrates how Nb$_{3}$Sn can be a good candidate for RF technological applications, also in high magnetic fields.Comment: ASC 2018 conference, accepted in IEEE Trans Appl Supercon

Echocardiography and Hemodynamic Monitoring Tools for Clinical Assessment of Patients on Mechanical Circulatory Support

Recent developments in ventricular assist devices have been quite remarkable. Rapid advances have been made particularly in terms of smaller size and more durable material and design. As a result, ventricular assist devices are increasingly being implanted in children and they are increasingly being used as a means of destination therapy for elderly patients with heart failure who are not eligible for heart transplantation. New issues have arisen as a result of these expanded indications. This book focuses on recent advances in ventricular assist devices itself and related issues

(s)INE: (soft-graft)-induced new entry tear after elephant trunk procedure

: Elephant trunk and frozen elephant trunk are established procedures for the treatment of aortic arch pathologies, such as aneurysm or dissection. The aim of open surgery is to re-expand the true lumen, favouring correct organ perfusion and the thrombosis of the false lumen. Frozen elephant trunk, with its stented endovascular portion, is sometimes associated with a life-threatening complication: the stent graft-induced new entry. In the literature, many studies reported the incidence of such issue after thoracic endovascular prosthesis or frozen elephant trunk, but in our knowledge, there are no case studies about the occurrence of stent graft-induced new entry with the use of soft grafts. For this reason, we decided to report our experience, highlighting how the use of a Dacron graft can cause distal intimal tears. We decided to coin the term soft-graft-induced new entry to indicate the development of an intimal tear induced by the soft prosthesis in the arch and proximal descending aorta

Levosimendan in critical illness: A literature review

Levosimendan, the active enantiomer of simendan, is a calcium sensitizer developed for treatment of decompensated heart failure, exerts its effects independently of the beta adrenergic receptor and seems beneficial in cases of severe, intractable heart failure. Levosimendan is usually administered as 24-h infusion, with or without a loading dose, but dosing needs adjustment in patients with severe liver or renal dysfunction. Despite several promising reports, the role of levosimendan in critical illness has not been thoroughly evaluated. Available evidence suggests that levosimendan is a safe treatment option in critically ill patients and may reduce mortality from cardiac failure. However, data from well-designed randomized controlled trials in critically ill patients are needed to validate or refute these preliminary conclusions. This literature review is an attempt to synthesize available evidence on the role and possible benefits of levosimendan in critically ill patients with severe heart failure

Left ventricular postoperative false aneurysm following apical venting

We report a case of false aneurysm of the left ventricle occurring subsequently to the placing of a vent sump line through the apex during an aortic valve procedure; the diagnosis was made twelve months later during a routine echocardiographic examination. The lesion was successfully repaired. This case recommend the use of other routes of venting in order to reduce the incidence of such complications

Measurement of gap between abutment and fixture in dental conical connection implants. A focused ion beam SEM observation

The aim of the authors was to examine the abutment-fixture interface in Morse-type conical implants in order to verify gaps at this level using a new microscopical approach. In this in vitro study, 20 abutment-fixture complexes were prepared by sectioning (longitudinal and cross-sectional to the long axis) with a microtome and then with a focused ion beam (FIB). This is a micrometric machine tool that uses gallium ions to abrade circumscribed areas to dig deeper into the cuts obtained with the microtome in order to eliminate cut-induced artifacts. This is because the FIB abrasion is practically free from artifacts, which are normally generated by the action of the microtome blades or other techniques. Samples were then observed by scanning electron microscopy (SEM). The observation of the abraded parts with the FIB permitted measurement of the real gap between the implant-abutment components. A variable amount of gap was retrieved (from 0 to 3 ?m) by the observations, confirming the non-hermetic nature of the connection. It has to be pointed out that in approximately 65% of cases, the gap accounted for less than 1 ?m. The reported data confirmed that the analyzed connection system allowed for minimal gap. However, from the evidence of the present analysis, it cannot be assumed that the 2 parts of a Morse-type conical implant are fused in 1 piece, which would create a perfectly matched hermetic connection

Microwave measurements of the high magnetic field vortex motion pinning parameters in Nb3_3Sn

The high frequency vortex motion in Nb$_3$Sn was analyzed in this work up to 12 T. We used a dielectric loaded resonator tuned at 15 GHz to evaluate the surface impedance $Z$ of a Nb$_3$Sn bulk sample (24.8 at.\%Sn). From the field induced variation of $Z$, the high frequency vortex parameters (the pinning constant $k_p$, the depinning frequency $\nu_p$ and the flux flow resistivity $\rho_{ff}$) were obtained over a large temperature and field range; their field and temperature dependence were analyzed. Comparison with other superconducting materials shows that high frequency applications in strong magnetic fields are also feasible with Nb$_3$Sn. In the present work, we report the first measurements about the microwave response in Nb$_3$Sn in strong magnetic fields.Comment: 24 pages, 12 figure

Fibroblast Interaction with Different Abutment Surfaces: In Vitro Study

Background: Attaining an effective mucosal attachment to the transmucosal part of the implant could protect the peri-implant bone. Aim: To evaluate if chair side surface treatments (plasma of Argon and ultraviolet light) may affect fibroblast adhesion on different titanium surfaces designed for soft tissue healing. Methods: Grade 5 titanium discs with four different surface topographies were subdivided into 3 groups: argon-plasma; ultraviolet light, and no treatment. Cell morphology and adhesion tests were performed at 20 min, 24 h, and 72 h. Results: Qualitative observation of the surfaces performed at the SEM was in accordance with the anticipated features. Roughness values ranged from smooth (MAC Sa = 0.2) to very rough (XA Sa = 21). At 20 min, all the untreated surfaces presented hemispherical cells with reduced filopodia, while the cells on treated samples were more spread with broad lamellipodia. However, these differences in spreading behavior disappeared at 24 h and 72 h. Argon-plasma, but not UV, significantly increased the number of fibroblasts independently of the surface type but only at 20 min. Statistically, there was no surface in combination with a treatment that favored a greater cellular adhesion. Conclusions: Data showed potential biological benefits of treating implant abutment surfaces with the plasma of argon in relation to early-stage cell adhesion

structural assessment of tf superconducting magnet of the dtt device

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