70 research outputs found
Residual mitral regurgitation after repair for posterior leaflet prolapse- Importance of preoperative anterior leaflet tethering
Background
Carpentier's techniques for degenerative posterior mitral leaflet prolapse have been established with excellent long‐term results reported. However, residual mitral regurgitation (
MR
) occasionally occurs even after a straightforward repair, though the involved mechanisms are not fully understood. We sought to identify specific preoperative echocardiographic findings associated with residual
MR
after a posterior mitral leaflet repair.
Methods and Results
We retrospectively studied 117 consecutive patients who underwent a primary mitral valve repair for isolated posterior mitral leaflet prolapse including a preoperative 3‐dimensional transesophageal echocardiography examination. Twelve had residual
MR
after the initial repair, of whom 7 required a corrective second pump run, 4 underwent conversion to mitral valve replacement, and 1 developed moderate
MR
within 1 month. Their preoperative parameters were compared with those of 105 patients who had an uneventful mitral valve repair. There were no hospital deaths. Multivariate analysis identified preoperative anterior mitral leaflet tethering angle as a significant predictor for residual
MR
(odds ratio, 6.82; 95% confidence interval, 1.8–33.8;
P
=0.0049). Receiver operator characteristics curve analysis revealed a cut‐off value of 24.3° (area under the curve, 0.77), indicating that anterior mitral leaflet angle predicts residual
MR
. In multivariate regression analysis, smaller anteroposterior mitral annular diameter (
P
<0.001) and lower left ventricular ejection fraction (
P
=0.002) were significantly associated with higher anterior mitral leaflet angle, whereas left ventricular and left atrial dimension had no significant correlation.
Conclusions
Anterior mitral leaflet tethering in cases of posterior mitral leaflet prolapse has an adverse impact on early results following mitral valve repair. The findings of preoperative 3‐dimensional transesophageal echocardiography are important for consideration of a careful surgical strategy.
</jats:sec
Real-time observation of picosecond-timescale optical quantum entanglement toward ultrafast quantum information processing
Entanglement is a fundamental resource of various optical
quantum-information-processing (QIP) applications. Towards high-speed QIP
system, entanglement should be encoded in short wavepackets. We report
real-time observation of ultrafast optical Einstein-Podolsky-Rosen (EPR)
correlation at a picosecond timescale in a continuous-wave (CW) system. Optical
phase-sensitive amplification using 6-THz-bandwidth
waveguide-optical-parametric amplifier enhances the effective efficiency of
70-GHz-bandwidth homodyne detectors, mainly used in 5th-generation
telecommunication, enabling its use in real-time quantum-state measurement.
While power measurement using frequency scanning, i.e., optical spectrum
analyzer, is not performed in real-time, our observation is demonstrated
through real-time amplitude measurement and can be directly employed in QIP
applications. Observed EPR states show quantum correlation of 4.5 dB below
shotnoise level encoded in wavepackets with 40-ps period, equivalent to 25-GHz
repetition -- times faster than previous entanglement observation in
CW system. The quantum correlation of 4.5 dB is already sufficient for several
QIP applications, and our system can be readily extended to large-scale
entanglement. Moreover, our scheme has high compatibility with optical
communication technology such as wavelength-division multiplexing, and
femtosecond-timescale observation is also feasible. Our demonstration is
paradigm shift in accelerating accessible quantum correlation, the foundational
resource of all quantum applications, from the nanosecond to picosecond
timescale, enabling ultra-fast optical QIP.Comment: 14 pages, 4 figure
High-rate Generation and State Tomography of Non-Gaussian Quantum States for Ultra-fast Clock Frequency Quantum Processors
Quantum information processors greatly benefit from high clock frequency to
fully harnessing the quantum advantages before they get washed out by the
decoherence. In this pursuit, all-optical systems offer unique advantages due
to their inherent 100 THz carrier frequency, permitting one to develop THz
clock frequency processors. In practice, the bandwidth of the quantum light
sources and the measurement devices has been limited to the MHz range and the
generation rate of nonclassical states to kHz order -- a tiny fraction of what
can be achieved. In this work, we go beyond this limitation by utilizing
optical parametric amplifier (OPA) as a squeezed-light source and optical
phase-sensitive amplifiers (PSA) to realize high-rate generation of broadband
non-Gaussian states and their quantum tomography. Our state generation and
measurement system consists of a 6-THz squeezed-light source, a 6-THz PSA, and
a 66-GHz homodyne detector. With this system, we have successfully demonstrated
non-Gaussian state generation at a 0.9 MHz rate -- almost three orders of
magnitude higher than the current state-of-the-art experiments -- with a
sub-nanosecond wave packet using continuous-wave laser. The performance is
constrained only by the superconducting detector's jitter which currently
limits the usable bandwidth of the squeezed light to 1 GHz, rather than the
optical and electronic systems. Therefore, if we can overcome the limitation of
the timing jitter of superconducting detector, non-Gaussian state generation
and detection at GHz rate, or even THz rate, for optical quantum processors
might be possible with OPAs.Comment: 17 pages, 5 figure
Austenite memory during reverse transformation of steels at different heating rates
The austenite (gamma) structure reversely transformed from martensite in Fe-0.55C mass% C alloy was investigated at high temperatures using in-situ an electron backscatter diffraction (EBSD) method. When the heating rate was varied, a rapidly heating produced fine gamma grains, in contrast, a slow heating induced coarse gamma grains having the same crystal orientations as those of the prior gamma grains; known as "gamma memory". The most likely mechanism for the gamma memory could be variant restrictions owing to cementite (theta). To investigate the effect of theta on the gamma memory, the sample was tempered at 700 degrees C for 24 h and theta was precipitated. The tempered sample exhibited the gamma memory irrespective of the heating rate. To clarify the origin of the gamma memory, we focused on the reversely transformed gamma formed adjacent to the theta and directly observed the orientation relationships (ORs) using the in-situ EBSD. A crystallographic analysis on the between neighboring ferrites (alpha), theta, and gamma revealed the existence of Kurdjumov-Sachs OR between gamma and two alpha (alpha 1 and alpha 2), Isaichev OR between alpha and theta, and Pitsch OR between theta and gamma. In the all possible combinations, the reversely transformed gamma satisfying the K-S OR for two alpha variants was limited to four variants. The theta variant satisfying the Isaichev OR for alpha 1 and alpha 2 was limited to one variant, which was close to one of the four variants by Pitsch OR, which suggests the gamma memory is due to these variant restrictions among alpha-theta-gamma
- …