1,721,302 research outputs found
Local density of states in metal-topological superconductor hybrid systems
Full text linkWe study by means of the recursive Green’s function technique the local density of states of (finite and semi-infinite) multiband spin-orbit-coupled semiconducting nanowires in proximity to an s-wave superconductor and attached to normal-metal electrodes. When the nanowire is coupled to a normal electrode, the zero-energy peak, corresponding to the Majorana state in the topological phase, broadens with increasing transmission between the wire and the leads, eventually disappearing for ideal interfaces. Interestingly, for a finite transmission a peak is present also in the normal electrode, even though it has a smaller amplitude and broadens more rapidly with
the strength of the coupling. Unpaired Majorana states can survive close to a topological phase transition even when the number of open channels (defined in the absence of superconductivity) is even. We finally study the Andreev-bound-state spectrum in superconductor-normal metal-superconductor junctions and find that in multiband nanowires the distinction between topologically trivial and nontrivial systems based on the number of zero-energy crossings is preserved
Reversal of compensatory flow in severe intrauterine growth restriction: middle cerebral artery and intracardiac volume flow modifications
No full textAIM:
The aim of the study was to investigate cerebral and cardiac volume flow modifications in a group of preterm severely growth restricted (GR) fetuses with absent end diastolic flow (AEDF) in the umbilical artery.
METHODS:
Doppler indices of GR fetuses born at less than 32 weeks of gestation with AEDF in umbilical artery were longitudinally analyzed. Ductus venosus S/A, umbilical artery PI, middle cerebral artery (MCA) pulsatility index (PI), MCA volume flow and intracardiac flows were checked daily. The value of volume flow was determined by multiplying the vessel area obtained by means of a power angiography by the integral of the velocimetric curve. In Group 1 the time of delivery was decided when abnormal Doppler index in ductus venosus (S/A>3) was detected. In Group 2, decisions about delivery were based on maternal indications or on various cardiotocographic (CTG) abnormalities. The division in the two groups was made with a retrospective method.
RESULTS:
Fifteen GR fetuses were studied: seven cases entered Group 1 and eight cases Group 2. In Group 2 velocimetric (PI) and quantitative (volume flow) values remained stable until delivery. In all cases in Group 1 ductus venosus anomalies (S/A>3) were preceded by 24 hours by cerebral volume flow indices indicating the loss of MCA vasodilatation and by changes in intracardiac volume flow indices, while the PI increase in MCA was present only 24 hours after the changes detected by the volume flow study and were simultaneous to ductus venosus modifications.
CONCLUSION:
The decrease in volume flow through the middle cerebral artery occurs at least 24 hours before the increase of middle cerebral artery PI and before the ductus venosus anomalies. Flow through the four cardiac valves show modification in agreement to the changes of the middle cerebral artery flow
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