108,384 research outputs found
Andreev States in long shallow SNS constrictions
We study Andreev bound states in a long shallow normal constriction, which is
open to a superconductor at both ends. The interesting features of such setup
include the absence of electron-hole symmetry and the interference of electron
waves along the constriction. We compare results of a numerical approach based
on the Bogoliubov equations with those of a refined semiclassical description.
Three types of Andreev bound states occur in the constriction: {\it i}) one
where both electron and hole wave part of the bound state propagate through the
constriction, {\it ii}) one where neither electron nor hole wave part
propagate, and {\it iii}) one where only the electron wave propagates. We show
that in a wide energy region the spacing between the Andreev states is strongly
modulated by the interference of electron waves passing the constriction
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Comparative effectiveness of drugs used to constrict the patent ductus arteriosus: a secondary analysis of the PDA-TOLERATE trial (NCT01958320).
ObjectiveTo evaluate the effectiveness of drugs used to constrict patent ductus arteriosus (PDA) in newborns < 28 weeks.MethodsWe performed a secondary analysis of the multi-center PDA-TOLERATE trial (NCT01958320). Infants with moderate-to-large PDAs were randomized 1:1 at 8.1 ± 2.1 days to either Drug treatment (n = 104) or Conservative management (n = 98). Drug treatments were assigned by center rather than within center (acetaminophen: 5 centers, 27 infants; ibuprofen: 7 centers, 38 infants; indomethacin: 7 centers, 39 infants).ResultsIndomethacin produced the greatest constriction (compared with spontaneous constriction during Conservative management): RR (95% CI) = 3.21 (2.05-5.01)), followed by ibuprofen = 2.03 (1.05-3.91), and acetaminophen = 1.33 (0.55-3.24). The initial rate of acetaminophen-induced constriction was 27%. Infants with persistent moderate-to-large PDA after acetaminophen were treated with indomethacin. The final rate of constriction after acetaminophen ± indomethacin was 60% (similar to the rate in infants receiving indomethacin-alone (62%)).ConclusionIndomethacin was more effective than acetaminophen in producing ductus constriction
Enhancement of polarization in a spin-orbit coupling quantum wire with a constriction
We investigate the enhancement of spin polarization in a quantum wire in the
presence of a constriction and a spin-orbit coupling segment. It is shown that
the spin-filtering effect is significantly heightened in comparison with the
configuration without the constriction. It is understood in the studies that
the constriction structure plays a critical role in enhancing the spin
filtering by means of confining the incident electrons to occupy one channel
only while the outgoing electrons occupy two channels. The enhancement of
spin-filtering has also been analyzed within the perturbation theory. Because
the spin polarization arises mainly from the scattering between the
constriction and the segment with spin-orbit coupling, the sub-band mixing
induced by spin-orbit interaction in the scattering process and the
interferences result in higher spin-filtering effect.Comment: 8 pages, 7 figure
Motor equivalent strategies in the production of /u/ in perturbed speech
Several articulatory strategies are available during the production of /u/, all resulting in a similar acoustic output. /u/ has two main constrictions, at the velum and at the lips. A perturbation of either constriction can be compensated at the other one, e.g wider constriction at the velum by more lip protrusion, wider lip opening by more tongue retraction. This study investigates whether speakers use this relation under perturbation. Six speakers were provided with palatal prostheses which were worn for two weeks. Speakers were instructed to make a serious attempt to produce normal speech. Their speech was recorded via EMA and acoustics several times over the adaptation period. Formant values of /u/-productions were measured. Velar constriction width and lip protrusion were estimated. For four speakers a correlation between constriction width and lip protrusion was found. A negative correlation between lip protrusion and F1 or F2 could sometimes be observed, but no correlation occurred between constriction size and either of the formants. The results show that under perturbation speakers use motor equivalent strategies in order to adapt. The correlation between constriction size and lip protrusion is stronger than in studies investigating unperturbed speech. This could be because under perturbation speakers are inclined to try out several strategies in order to reach the acoustic target and the co-variability might thus be greater
Capsaicin-Induced Ca2+ Influx and Constriction of the Middle Meningeal Artery
Research in the past on transient receptor potential cation channel subfamily V member 1 (TRPV1) has been limited to mainly nervous tissue TRPV1 because of the channel’s role in pain perception. Here, we studied the potential role of TRPV1 in vascular smooth muscle. We have observed that capsaicin, a TRPV1 agonist, induced constriction of the middle meningeal artery (MMA). Our goal was to decipher the mechanism of capsaicin-induced constriction of the MMA. Arterial diameter measurements showed that constriction due to 100 nM capsaicin (65.4% ± 3.7, n=7) was significantly diminished in the presence of the voltage-dependent calcium channel (VDCC) blocker 100 µM diltiazem (43.1% ± 8.1, n=7). Capsaicin-induced constriction was not significantly altered in the presence of the sarco/endoplasmic reticulum calcium transport ATPase (SERCA) inhibitor 30 µM cyclopiazonic acid (63.7 ± 9.0%, n=5) compared to control arteries (58.4 ± 8.6%, n=5). The unaltered capsaicin-induced constriction of the MMA in the presence of a SERCA inhibitor suggests that calcium-induced calcium release does not contribute to the overall calcium influx mechanism within the smooth muscle cells of the MMA. The diminished capsaicin-induced constriction of the MMA in the presence of a VDCC blocker suggests that sodium entry through TRPV1 channels can possibly lead to the membrane potential depolarization and increased activity of VDCCs causing further calcium influx. Furthermore, since the capsaicin effect was not abolished by the blockage of VDCCs, our data suggest that calcium entry through TRPV1 is sufficient to cause approximately 65% of the total constriction of the MMA in response to activation of TRPV1
Discontinuous resistance change and domain wall scattering in patterned NiFe wires with a nanoconstriction
A nonlinear current-voltage (I-V) characteristic was observed in patterned NiFe wires with a central "bow-tie" point contact constriction. By passing a dc current through the wire, a sharp resistance drop was obtained for current densities in the range of 1.1-1.4 x 10(7) A/cm(2). This is attributed to current-induced domain wall drag, resulting in displacement of a domain wall away from the constriction. A maximum current-induced resistance change of 0.079% was obtained for a 100-nm constriction, which is comparable with the magnetoresistance due to domain wall scattering in NiFe
Exploiting Locally Imposed Anisotropies in (Ga,Mn)As: a Non-volatile Memory Device
Progress in (Ga,Mn)As lithography has recently allowed us to realize
structures where unique magnetic anisotropy properties can be imposed locally
in various regions of a given device. We make use of this technology to
fabricate a device in which we study transport through a constriction
separating two regions whose magnetization direction differs by 90 degrees. We
find that the resistance of the constriction depends on the flow of the
magnetic field lines in the constriction region and demonstrate that such a
structure constitutes a non-volatile memory device
Forced transport of deformable containers through narrow constrictions
We study, numerically and analytically, the forced transport of deformable
containers through a narrow constriction. Our central aim is to quantify the
competition between the constriction geometry and the active forcing,
regulating whether and at which speed a container may pass through the
constriction and under what conditions it gets stuck. We focus, in particular,
on the interrelation between the force that propels the container and the
radius of the channel, as these are the external variables that may be directly
controlled in both artificial and physiological settings. We present
Lattice-Boltzmann simulations that elucidate in detail the various phases of
translocation, and present simplified analytical models that treat two limiting
types of these membrane containers: deformational energy dominated by the
bending or stretching contribution. In either case we find excellent agreement
with the full simulations, and our results reveal that not only the radius but
also the length of the constriction determines whether or not the container
will pass.Comment: 9 pages, 4 figure
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