Valve Tunnel Research Articles

Postoperative high astigmatism - Refractive surprise following manual small-incision cataract surgery

Postoperative astigmatism plays an important role in the final visual outcome of cataract surgery. In small-incision cataract surgery, proper tunnel construction is of utmost importance for good structural integrity, leading to sutureless self-sealing wounds with lesser astigmatism. We report a case of postoperative high astigmatism following manual small-incision cataract surgery due to large, irregular, superficial, and more anterior corneal entry that lead to poor tunnel valve effect and wound sagging. This resulted in a poor postoperative unaided visual outcome.

Resonant enhancement of damping within the free layer of a microscale magnetic tunnel valve

Picosecond magnetization dynamics in the free and pinned layers of a microscale magnetic tunnel valve have been studied using time-resolved scanning Kerr microscopy. A comparison of the observed dynamics with those of individual free and pinned layers allowed the effect of interlayer coupling to be identified. A weak interlayer coupling in the tunnel valve continuous film reference sample was detected in bulk magnetometry measurements, while focused Kerr magnetometry showed that the coupling was well maintained in the patterned structure. In the tunnel valve, the free layer precession was observed to have reduced amplitude and an enhanced relaxation. During magnetization reversal in the pinned layer, its frequency approached that of the low frequency mode associated with the free layer. At the pinned layer switching field, the linewidth of the free layer became similar to that of the pinned layer. The similarity in their frequencies promotes the formation of precessional modes that exhibit strong collective properties such as frequency shifting and enhanced linewidth, while inhomogeneous magnetization of the pinned layer during reversal may also play a role in these observations. The collective character of precessional dynamics associated with mixing of the free and pinned layer magnetization dynamics must be accounted for even in tunnel valves with a small interlayer coupling.

Tunnel Valve Sensors in Contact Recording

Results of experiments in which hard-disk drive (HDD) tunnel valve (TV) sensors were run in continuous contact with magnetic recording tape are presented. In one mode, suspended HDD sliders were run against tape backed by a supporting air film in a novel configuration. In another, tape was run in an air-skiving mode over HDD rowbars mounted on support beams, similar to the way tape wraps a conventional tape head. The data indicate that HDD TV sensors can successfully operate in continuous contact with running tape media. Measurements show that roughness of older generation metal particle tape limits the signal-to-noise ratio achievable using existing narrow HDD TV sensors. However, TV sensors optimized for running on smoother barium ferrite tape are now a viable candidate for future high areal density tape recording platforms.

Nanophysics and nanotechnology applied to sensors, part 1

Miniaturization is a reliable recipe toward higher efficiency and lower cost of sensors and has fortunately led to the discovery of entirely new devices. Quantum mechanical effects tend to appear as the size of devices decrease. In the development of higher performing computer chips, a deleterious quantum effect, tunneling leakage through the gate insulator, was circumvented, by use of "high kappa oxides". In a very important case, a new sensor, the magnetic tunnel junction, is an entirely "nanophysical" device. The magnetic tunnel junction MTJ or "tunnel valve" sensor has greatly improved disk drive performance and has had a large economic impact. Nano sized components, such as the carbon nanotube, permit novel sensors and can sense polar molecules. Even optical detection of single virus particles is possible and was described.

Simple theory of hot electron dynamics observed by femtosecond ellipsometry

The dynamics of the linear and angular momenta of hot electrons in metals are of key importance for the design and operation of hot electron devices such as spin and tunnel valve transistors. The corresponding relaxation times are expected to lie in the subpicosecond range and must be studied with experimental techniques of adequate (femtosecond) temporal resolution. Here we report a simple theory of the ultrafast ellipsometric response of metals after excitation with femtosecond optical pulses. Although developed in the relaxation time approximation, the theory allows electron linear and angular momentum relaxation times to be extracted.

A SEROUS LINED ANTIREFLUX VALVE: IN VIVO FLUOROURODYNAMIC EVALUATION OF ANTIREFLUX CONTINENCE MECHANISM

Purpose We evaluate the fluoroscopic and urodynamic performance of a new serosal lined antireflux continence valve (T pouch valve) using an in vivo animal model. Materials and Methods Intestinal reservoirs were constructed using an in vivo pig model. Multiple serosal lined valves of varying diameters and tunnel lengths were evaluated in the acute (immediately after construction) and chronic (4 weeks postoperatively) settings. Video fluorourodynamic evaluations were performed to identify valve leak point pressures and optimal tunnel length-to-luminal diameter ratios. Results Four serosal lined valves tapered to a diameter of 18 and 30F in 1 and 2 cm. tunnels were evaluated. Immediately following construction of the valves no leakage was observed during reservoir filling (maximal pressure 50 cm. water) or external compression maneuvers to simulate a Valsalva maneuver (maximal intra-reservoir pressure 100 cm. water). Identical fluorourodynamic studies performed after a 4-week recuperation demonstrated leakage through the 30F, 1 cm. tunnel valve during reservoir filling (intra-reservoir pressure 19 cm. water). Increasing the tunnel length of the 30F system to 2 cm. (tunnel length-to-luminal diameter ratio 2:1) eliminated all evidence of valve leakage up to a maximal intra-reservoir pressure of 100 cm. water. Conclusions These studies demonstrate the urodynamic characteristics of a new serosal lined valve. This easily constructed mechanism serves as a reliable antireflux (afferent) or continence (efferent) system.

Noniterative System Identification Applied to Wind Tunnel Valve Control

A noniterative system identification procedure is developed and applied to the air supply control valves of a wind tunnel. These control valves regulate the air flow through the wind tunnel and thereby determine the flight conditions being simulated. The position control system for these valves must be of high performance and should be maintained in a properly tuned condition.

Investigations of Transonic Ludwieg Tubes : Part3 Effects of Plenum Exhaust System on Starting Process of Tunnel Test Section

The starting time of a transonic Ludwieg tube is dependent on the timing of opening the main tunnel valve and the plenum exhaust valve, as well as the plenum chamber volume, the exhaust rate, the opening times of the main and the exhaust valves, and so on. In the previous paper, the starting process of the transonic Ludwieg tube with a main valve downstream of the transonic test section was studied in the case that the main and the exhaust valves started to open simultaneously. In the present paper, starting to open the plenum exhaust valve was delayed or advanced from the opening of the main valve, and the effect of plenum exhaust delays on the staring time of the transonic test section was discussed. Further, the effect of the orifice position in the plenum exhaust system on the starting time was experimentally investigated. The starting time becomes a little smaller by locating the orifice at the downstream section of the exhaust valve.