133 research outputs found
Shear-Flow Driven Current Filamentation: Two-Dimensional Magnetohydrodynamic Simulations
The process of current filamentation in permanently externally driven,
initially globally ideal plasmas is investigated by means of two-dimensional
Magnetohydrodynamic (MHD)-simulations. This situation is typical for
astrophysical systems like jets, the interstellar and intergalactic medium
where the dynamics is dominated by external forces. Two different cases are
studied. In one case, the system is ideal permanently and dissipative processes
are excluded. In the second case, a system with a current density dependent
resistivity is considered. This resistivity is switched on self-consistently in
current filaments and allows for local dissipation due to magnetic
reconnection. Thus one finds tearing of current filaments and, besides, merging
of filaments due to coalescence instabilities. Energy input and dissipation
finally balance each other and the system reaches a state of constant magnetic
energy in time.Comment: 32 Pages, 13 Figures. accepted, to appear in Physics of Plasmas
(049012
Large-bore Vascular Closure: New Devices and Techniques
Endovascular aneurysm repair, transcatheter aortic valve implantation and percutaneous mechanical circulatory support systems have become valuable alternatives to conventional surgery and even preferred strategies for a wide array of clinical entities. Their adoption in everyday practice is growing. These procedures require large-bore access into the femoral artery. Their use is thus associated with clinically significant vascular bleeding complications. Meticulous access site management is crucial for safe implementation of large-bore technologies and includes accurate puncture technique and reliable percutaneous closure devices. This article reviews different strategies for obtaining femoral access and contemporary percutaneous closure technologies
The critical velocity effect as a cause for the H\alpha emission from the Magellanic stream
Observations show significant H\alpha-emissions in the Galactic halo near the
edges of cold gas clouds of the Magellanic Stream. The source for the
ionization of the cold gas is still a widely open question. In our paper we
discuss the critical velocity effect as a possible explanation for the observed
H\alpha-emission. The critical velocity effect can yield a fast ionization of
cold gas if this neutral gas passes through a magnetized plasma under suitable
conditions. We show that for parameters that are typical for the Magellanic
Stream the critical velocity effect has to be considered as a possible
ionization source of high relevance.Comment: 9 pages, 2 figures. accepted, to appear in The Astrophysical Journa
Insights in a restricted temporary pacemaker strategy in a lean transcatheter aortic valve implantation program
OBJECTIVES: To study the safety and feasibility of a restrictive temporaryâRVâpacemaker use and to evaluate the need for temporary pacemaker insertion for failed left ventricular (LV) pacing ability (no ventricular capture) or occurrence of highâdegree AVâblocks mandating continuous pacing. BACKGROUND: Ventricular pacing remains an essential part of contemporary transcatheter aortic valve implantation (TAVI). A temporaryârightâventricle (RV)âpacemaker lead is the standard approach for transient pacing during TAVI but requires central venous access. METHODS: An observational registry including 672 patients who underwent TAVI between June 2018 and December 2020. Patients received pacing on the wire when necessary, unless there was a highâanticipated risk for conduction disturbances postâTAVI, based on the baselineâECG. The followâup period was 30âdays. RESULTS: A temporaryâRVâpacemaker lead (RVPâcohort) was inserted in 45 patients, pacing on the wire (LVPâcohort) in 488 patients, and no pacing (NoPâcohort) in 139 patients. A bailout temporary pacemaker was implanted in 14 patients (10.1%) in the NoPâcohort and in 24 patients (4.9%) in the LVPâcohort. One patient in the LVPâcohort needed an RVâpacemaker for incomplete ventricular capture. Procedure time was significantly longer in the RVPâcohort (68âmin [IQR 52â88.] vs. 55âmin [IQR 44â72] in NoPâcohort and 55âmin [IQR 43â71] in the LVPâcohort [pâ<â0.005]). Procedural highâdegree AVâblock occurred most often in the RVPâcohort (45% vs. 14% in the LVP and 16% in the NoPâcohort [pââ€â0.001]). Need for new PPI occurred in 47% in the RVPâcohort, versus 20% in the NoPâcohort and 11% in the LVPâcohort (pââ€â0.001). CONCLUSION: A restricted RVâpacemaker strategy is safe and shortens procedure time. The majority of TAVIâprocedures do not require a temporaryâRVâpacemaker
A new variational approach to the stability of gravitational systems
We consider the three dimensional gravitational Vlasov Poisson system which
describes the mechanical state of a stellar system subject to its own gravity.
A well-known conjecture in astrophysics is that the steady state solutions
which are nonincreasing functions of their microscopic energy are nonlinearly
stable by the flow. This was proved at the linear level by several authors
based on the pioneering work by Antonov in 1961. Since then, standard
variational techniques based on concentration compactness methods as introduced
by P.-L. Lions in 1983 have led to the nonlinear stability of subclasses of
stationary solutions of ground state type.
In this paper, inspired by pioneering works from the physics litterature
(Lynden-Bell 94, Wiechen-Ziegler-Schindler MNRAS 88, Aly MNRAS 89), we use the
monotonicity of the Hamiltonian under generalized symmetric rearrangement
transformations to prove that non increasing steady solutions are local
minimizer of the Hamiltonian under equimeasurable constraints, and extract
compactness from suitable minimizing sequences. This implies the nonlinear
stability of nonincreasing anisotropic steady states under radially symmetric
perturbations
Clinical consequences of consecutive self-expanding transcatheter heart valve iterations
OBJECTIVE: To compare early clinical outcomes after transcatheter aortic valve implantation (TAVI) with three consecutive generations of self-expanding valves (SEVs). METHODS: Clinical endpoints of consecutive patients who underwent TAVI with CoreValve, Evolut R or Evolut PRO were included in a prospective database. RESULTS: TAVI was performed with CoreValve (nâŻ=â116), Evolut R (nâŻ=â160) or Evolut PRO (nâŻ=â92). Evolut R and Evolut PRO showed a tendency towards lower permanent pacemaker implantation (PPI) rates compared to CoreValve (CoreValve 27% vs Evolut R 16% vs Evolut PRO 18%, pâŻ=â0.091). By multivariable regression analysis CoreValve had a significantly higher risk for PPI (odds ratio (OR) 2.79, 95% confidence interval (CI) 1.31â5.94, pâŻ=â0.008) compared to Evolut R, while Evolut R and PRO were similar. Severe paravalvular leakage (PVL) occurred only with CoreValve, but no significant difference was observed in moderate PVL (10% vs 8% vs 6%, pâŻ=â0.49). CoreValve had a tendency towards a higher risk for more-than-mild PVL as compared with the Evolut platform (RâŻ+âPRO) (OR 2.46, 95% CI 0.98â6.16, pâŻ=â0.055). No significant differences in all-cause mortality (7% vs 4% vs 1%, pâŻ=â0.10), stroke (6% vs 3% vs 2%, pâŻ=â0.21) or major vascular complications (10% vs 12% vs 4%, pâŻ=â0.14) were observed. CONCLUSIONS: TAVI with self-expanding valves was safe, and device iterations may result in a lower need for PPI. More-than-mild PVL seemed to occur less often with repositionable technology. SUPPLEMENTARY INFORMATION: The online version of this article (10.1007/s12471-021-01568-5) contains supplementary material, which is available to authorized users
Milestones in the Observations of Cosmic Magnetic Fields
Magnetic fields are observed everywhere in the universe. In this review, we
concentrate on the observational aspects of the magnetic fields of Galactic and
extragalactic objects. Readers can follow the milestones in the observations of
cosmic magnetic fields obtained from the most important tracers of magnetic
fields, namely, the star-light polarization, the Zeeman effect, the rotation
measures (RMs, hereafter) of extragalactic radio sources, the pulsar RMs, radio
polarization observations, as well as the newly implemented sub-mm and mm
polarization capabilities.
(Another long paragraph is omitted due to the limited space here)Comment: Invited Review (ChJA&A); 32 pages. Sorry if your significant
contributions in this area were not mentioned. Published pdf & ps files (with
high quality figures) now availble at http://www.chjaa.org/2002_2_4.ht
Caveolin 1 protein expression in renal cell carcinoma predicts survival
<p>Abstract</p> <p>Background</p> <p>Caveolae play a significant role in disease phenotypes such as cancer, diabetes, bladder dysfunction, and muscular dystrophy. The aim of this study was to elucidate the caveolin-1 <it>(</it>CAV1<it>) </it>protein expression in renal cell cancer (RCC) and to determine its potential prognostic relevance.</p> <p>Methods</p> <p>289 clear cell RCC tissue specimens were collected from patients undergoing surgery for renal tumors. Both cytoplasmic and membranous CAV1 expression were determined by immunohistochemistry and correlated with clinical variables. Survival analysis was carried out for 169 evaluable patients with a median follow up of 80.5 months (interquartile range (IQR), 24.5 - 131.7 months).</p> <p>Results</p> <p>A high CAV1 expression in the tumor cell cytoplasm was significantly associated with male sex (p = 0.04), a positive nodal status (p = 0.04), and poor tumor differentiation (p = 0.04). In contrast, a higher than average (i.e. > median) CAV1 expression in tumor cell membranes was only linked to male sex (p = 0.03). Kaplan-Meier analysis disclosed significant differences in 5-year overall (51.4 vs. 75.2%, p = 0.001) and tumor specific survival (55.3 vs. 80.1%, p = 0.001) for patients with higher and lower than average cytoplasmic CAV1 expression levels, respectively. Applying multivariable Cox regression analysis a high CAV1 protein expression level in the tumor cell cytoplasm could be identified as an independent poor prognostic marker of both overall (p = 0.02) and tumor specific survival (p = 0.03) in clear cell RCC patients.</p> <p>Conclusion</p> <p>Over expression of caveolin-1 in the tumour cell cytoplasm predicts a poor prognosis of patients with clear cell RCC. CAV1 is likely to be a useful prognostic marker and may play an important role in tumour progression. Therefore, our data encourage further investigations to enlighten the role of CAV1 and its function as diagnostic and prognostic marker in serum and/or urine of RCC patients.</p
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