386 research outputs found

    High Curie temperature Mn 5 Ge 3 thin films produced by non-diffusive reaction

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    Polycrystalline Mn 5 Ge 3 thin films were produced on SiO 2 using magnetron sputtering and reactive diffusion (RD) or non-diffusive reaction (NDR). In situ X-ray diffraction and atomic force microscopy were used to determine the layer structures, and magnetic force microscopy, superconducting quantum interference device and ferromagnetic resonance were used to determine their magnetic properties. RD-mediated layers exhibit similar magnetic properties as MBE-grown monocrystalline Mn 5 Ge 3 thin films, while NDR-mediated layers show magnetic properties similar to monocrystalline C-doped Mn 5 Ge 3 C x thin films with 0.1x0.2.0.1 \leq x \leq 0.2. NDR appears as a CMOS-compatible efficient method to produce good magnetic quality high-curie temperature Mn 5 Ge 3 thin films

    Large-scale bottleneck effect in two-dimensional turbulence

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    The bottleneck phenomenon in three-dimensional turbulence is generally associated with the dissipation range of the energy spectrum. In the present work, it is shown by using a two-point closure theory, that in two-dimensional turbulence it is possible to observe a bottleneck at the large scales, due to the effect of friction on the inverse energy cascade. This large-scale bottleneck is directly related to the process of energy condensation, the pile-up of energy at wavenumbers corresponding to the domain size. The link between the use of friction and the creation of space-filling structures is discussed and it is concluded that the careless use of hypofriction might reduce the inertial range of the energy spectrum

    Optimal estimation for Large-Eddy Simulation of turbulence and application to the analysis of subgrid models

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    The tools of optimal estimation are applied to the study of subgrid models for Large-Eddy Simulation of turbulence. The concept of optimal estimator is introduced and its properties are analyzed in the context of applications to a priori tests of subgrid models. Attention is focused on the Cook and Riley model in the case of a scalar field in isotropic turbulence. Using DNS data, the relevance of the beta assumption is estimated by computing (i) generalized optimal estimators and (ii) the error brought by this assumption alone. Optimal estimators are computed for the subgrid variance using various sets of variables and various techniques (histograms and neural networks). It is shown that optimal estimators allow a thorough exploration of models. Neural networks are proved to be relevant and very efficient in this framework, and further usages are suggested

    Extrinsic outflow graft flow obstruction in patients with HeartMate3 LVAD

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    Blood flow obstruction at the level of the outflow graft is a rare but severe complication of LVAD support. We present a series of five patients supported with HeartMate3 LVAD (Abbott Labs, Chicago, IL) that developed an outflow graft obstruction after 607–1250 days of support, during prolonged antithrombotic therapy. Three patients presented with severe symptoms of heart failure, were treated with endovascular stenting and experienced full recovery. Preoperative computed tomography angiography and intraoperative angiography together with intravascular ultrasound provided diagnosis and guided treatment. In two patients, outflow obstruction was an occasional finding at imaging without heart failure symptoms and a “watchful waiting” approach was adopted: delayed treatment in one of them was futile. This late adverse event is peculiar for its pathophysiology and not yet discussed among the mechanical circulatory support community

    Sentinel lymph node biopsy in porocarcinoma: A case reports

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    Introduction: Eccrine porocarcinoma (EPC) is a slow-growing carcinoma arising from the eccrine sweat glands. Based on its clinical presentation it can be confused with malignant and benign skin lesions, both. Histological examination is essential to formulate a correct diagnosis. Surgical excision with clear margins is the standard therapeutic approach while the role of sentinel lymph node biopsy (SNLB) remains controversial. Case presentation: The Authors report two cases of EPC of the lower limbs occurred in two women. Patients were treated by wide surgical excision of the lesion and SNLB. 6 months follow-up was disease free for both patients. Conclusion: Although a rare cutaneous tumor, EPC has to be taken into account in the differential diagnosis of malignant skin lesions because of its possible loco-regional aggressiveness and related morbidity. Among the available treatment options, surgical excision is considered the standard approach whereas the role of SNLB is controversial although the Authors discuss a possible usefulness for staging and diagnosis

    Emergent endovascular treatment options for thoracoabdominal aortic aneurysm

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    For a long time, parallel grafting, physician-modified endografts, and, more recently, in situ fenestration were the only go-to endovascular options for ruptured thoracoabdominal aortic aneurysm, offered mixed results, and depended mainly on the operator's and center's experience. As custom-made devices have become an established endovascular treatment option for elective thoracoabdominal aortic aneurysm, they are not a viable option in the emergency setting, as endograft production can take up to 4 months. The development of off-the-shelf (OTS) multibranched devices with a standardized configuration has allowed the treatment of ruptured thoracoabdominal aortic aneurysm with emergent branched endovascular procedures. The Zenith t-Branch device (Cook Medical) was the first readily available graft outside the United States to receive the CE mark (in 2012) and is currently the most studied device for those indications. A new device, the E-nside thoracoabdominal branch endoprosthesis OTS multibranched endograft (Artivion), has been made commercially available, and the GORE EXCLUDER thoracoabdominal branch endoprosthesis OTS multibranched endograft (W. L. Gore and Associates) is expected to be released in 2023. Due to the lack of guidelines on ruptured thoracoabdominal aortic aneurysm, this review summarizes the available treatment options (ie, parallel grafts, physician-modified endografts, in situ fenestrations, and OTS multibranched devices), compares the indications and contraindications, and points out the evidence gaps that should be filled in the next decade

    Calcium-phosphate glass-based bioresorbable fibre optics for light and drug delivery

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    Calcium-phosphate glasses (CPGs) are commonly used as scaffolds in tissue engineering. A novel formulation of optically transparent CPG has been recently developed to be used as an optical fibre for biomedical implantable devices. Its purpose is to combine the bioresorbability of CPGs with optical features, thus extending the applications of bioresorbable sensors for in-body monitoring or diagnostics. Modifications of the glass composition or post-treatments on the fibres can tailor the dissolution time and the interaction of the glass with different stimuli as well as with specific cells. The tested glasses both in bulk and fibre shapes showed good strength (from 200 to 350 MPa) with values that are lower than standard silica glass and much higher than common bioresorbable polymers. CPG fibres were also implanted in living rats for several weeks and no clinical signs of any adverse effect have been found. We will present our latest results on these subjects starting from the characterisation of the CPGs by means of dissolution tests, in-vitro, and ex-vivo experiments

    A scoping review on the approaches for cannulation of reno-visceral target vessels during complex endovascular aortic repair

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    OBJECTIVES: The aim of this study was to assess the approaches to reno-visceral target vessels (TVs) cannulation during branched-fenestrated endovascular aortic repair, determine the evidence base that links these approaches to clinical outcomes and identify literature gaps. METHODS: A scoping review following the PRISMA Protocols Extension for Scoping Reviews was performed. Available full-text studies published in English (PubMed, Cochrane and EMBASE databases; last queried, 31 June 2022) were systematically reviewed and analysed. Data were reported as descriptive narrative or tables, without any statistical analysis nor quality assessment. RESULTS: Fourteen retrospective articles were included. Seven articles studied the use of upper extremity access (UEA) during branched-fenestrated endovascular aortic repair, 3 studied the use of steerable sheaths and 4 included both approaches. A left UEA was used in 757 patients (technical success: 99%, stroke rate: 1-3%) and a right UEA in 215 patients (technical success: 92-98%, stroke rate: 0-13%). Seven studies (1066 patients) described a surgical access only (technical success: 80-99%, stroke rate: 0-13%), while 3 studies (146 patients) described a percutaneous access only (technical success: 83-90%, stroke rate: 3%) and lastly 4 studies compared UEA versus use of steerable sheaths from the transfemoral approach (TFA) (UEA: 563 patients, technical success: 95-98%, stroke rate: 1-8%; TFA: 209 patients, technical success: 98-100%, stroke rate: 0-1%). CONCLUSIONS: Both UEA and TFA as cannulation approaches were associated with high technical success and low perioperative complications. Currently, there is a paucity of high-quality data to provide definitive indication. Optimal UEA in terms of side (left versus right) and approach (surgical versus percutaneous) needs further study

    Turbulence and Radio Mini-halos in the Sloshing Cores of Galaxy Clusters

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    A number of relaxed, cool-core galaxy clusters exhibit diffuse, steep-spectrum radio sources in their central regions, known as radio mini-halos. It has been proposed that the relativistic electrons responsible for the emission have been reaccelerated by turbulence generated by the sloshing of the cool core gas. We present a high-resolution MHD simulation of gas sloshing in a galaxy cluster coupled with subgrid simulations of relativistic electron acceleration to test this hypothesis. Our simulation shows that the sloshing motions generate turbulence on the order of δv\delta{v} \sim 50-200 km s1^{-1} on spatial scales of \sim50-100 kpc and below in the cool core region within the envelope of the sloshing cold fronts, whereas outside the cold fronts, there is negligible turbulence. This turbulence is potentially strong enough to reaccelerate relativistic electron seeds (with initial γ100500\gamma \sim 100-500) to γ104\gamma \sim 10^4 via damping of magnetosonic waves and non-resonant compression. The seed electrons could remain in the cluster from, e.g., past AGN activity. In combination with the magnetic field amplification in the core, these electrons then produce diffuse radio synchrotron emission that is coincident with the region bounded by the sloshing cold fronts, as indeed observed in X-rays and the radio. The result holds for different initial spatial distributions of preexisting relativistic electrons. The power and the steep spectral index (α12\alpha \approx 1-2) of the resulting radio emission are consistent with observations of minihalos, though the theoretical uncertainties of the acceleration mechanisms are high. We also produce simulated maps of inverse-Compton hard X-ray emission from the same population of relativistic electrons.Comment: 28 pages, 29 figures, in emulateapj format. Revised version accepted by the referee, conclusions unchange
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