Artificial Ring Research Articles

Isolated Unilateral Agenesis of the Pulmonary Artery: Surgical Repair With an Artificial Graft

This report describes a 3-month-old Japanese boy with a diagnosis of isolated unilateral agenesis of the proximal right pulmonary artery with severe pulmonary hypertension. One-stage reconstruction of the right pulmonary artery was performed without cardiopulmonary bypass. The hilar right pulmonary artery and the distal main pulmonary artery were joined by anastomosis to an artificial ring graft. The boy's postoperative course was uneventful, and the pressure in the pulmonary artery was within the normal range. Although mild right pulmonary artery stenosis remained, the authors' therapeutic strategy may provide a clinically important option for isolated unilateral agenesis of the pulmonary artery.

Unique metallurgical microstructures and characteristics of nano-amorphous state bulk alloys formed under high gravity by very high speed centrifugal casting

ABSTRACTAn innovative “Rapid-Solidification Centrifugal Casting (RSCC) Process” was applied to manufacturing more high functional Fe-based magnetic alloys and some amorphous bulk metallic glassy alloys (BMGs) components. The molten alloys were poured into copper mold with rotation speed up to 6000rpm which can cause the maximum 4000 times as much centrifugal pressurization force as gravity. The bulk components of ring or very small three dimensional component samples of Fe and Zr alloy systems were successfully fabricated within only a few seconds at one process from melts with more cheap production cost. The molten raw BMG alloys (ZrAl system) and Fe-based soft-magnetic alloys(FeGaAl and FeSiB systems) by high frequency induction heating method were poured into copper mold. The fabricated BMG components of artificial tooth and ring of ZrAlNiCu alloy system are almost amorphous state by XRD profiles. Especially, the soft magnetic properties of two Fe-based alloys showed drastic change and were enhanced generally depending on the unique very fine, nano-scale columnar grains with strong texture toward radius direction for FeGaAl(Galfenol) alloy. The magnetization saturation Bs was enhanced up to1.97T in FeSiBPCu alloy. In consequence, according to synergistic effect of rapid solidification and high pressurization casting in this manufacturing process, RSCCP has the technical advantages of expansion of element composition, uniformity of the quality, reduction of internal defects and prevention of degradation at the time of secondary fabrication process of nano-crystalline-structured alloys and BMGs.

新たな人工弁輪Ｐｈｙｓｉｏリング‐ＩＩを用いた僧帽弁形成術

今回，新たに開発された Physio リング-II により僧帽弁形成術を行なった経験を報告する．Phyio リング-II は，Physio リングを改良した人工弁輪で，セミリジッド構造とダブルサドルシェイプ構造をもつ．対象はPhysio リング-II により僧帽弁形成術を施行した 4 例とした．手術死亡，術後合併症はなく，術後 NYHA class分類は全例 I 度に改善した．術後僧帽弁逆流は，2 例がtrivial，2 例は全く認められなかった．術後 LDH は全例正常範囲で，溶血を疑わせる症例はなかった．Phyio リング-II は生理的な弁輪構造をもつ人工弁輪で，僧帽弁形成術の可能性をより広げるものであると考えられた．

The creation of the artificial RING finger from the cross-brace zinc finger by α-helical region substitution

The creation of the artificial RING finger as ubiquitin-ligating enzyme (E3) has been demonstrated. In this study, by the α-helical region substitution between the EL5 RING finger and the Williams–Beuren syndrome transcription factor (WSTF) PHD finger, the artificial E3 (WSTF PHD_RING finger) was newly created. The experiments of the chemical modification of residues Cys and the circular dichroism spectra revealed that the WSTF PHD_RING finger binds two zinc atoms and adopts the zinc-dependent ordered-structure. In the substrate-independent ubiquitination assay, the WSTF PHD_RING finger functions as E3 and was poly- or mono-ubiquitinated. The present strategy is very simple and convenient, and consequently it might be widely applicable to the creation of various artificial E3 RING fingers with the specific ubiquitin-conjugating enzyme (E2)-binding capability.

Active infective endocarditis after mitral valve repair

A 22-year-old man was diagnosed with active mitral endocarditis 14 months after mitral valve repair. The responsible organism was methicillin-resistant Staphylococcus epidermidis. Transthoracic echocardiography showed an 8-mm patch of vegetation adhering to the anterior part of the artificial ring. Although antibiotics (piperacillin, minocycline, imipenem/cilastatin, and ampicillin) were administered, the vegetation grew to 30 mm. Reoperation was performed 35 days after the diagnosis. Before surgery, there was mild mitral regurgitation without congestive heart failure. Re-repair was performed by removing the vegetation and the artificial ring, and mattress sutures repaired the circumferential sulcus formed by the artificial ring. Teicoplanin and minocycline were administered for 6 weeks. At 20 months, infective endocarditis was absent. Residual mitral regurgitation has been consistently mild. Although active mitral endocarditis after mitral valve repair is rare, prompt reoperation should be considered if the responsible organism is drug-resistant and infection spreads to the artificial ring.

Artificial molecular quantum rings under magnetic field influence

The ground states of a few electrons confined in two vertically coupled quantum rings in the presence of an external magnetic field are studied systematically within the current spin-density functional theory. Electron-electron interactions combined with inter-ring tunneling affect the electronic structure and the persistent current. For small values of the external magnetic field, we recover the zero magnetic field molecular quantum ring ground state configurations. Increasing the magnetic field many angular momentum, spin, and isospin transitions are predicted to occur in the ground state. We show that these transitions follow certain rules, which are governed by the parity of the number of electrons, the single-particle picture, Hund’s rules, and many-body effects.

Reconstruction of a friable posterior mitral annulus after removing a calcified artificial ring using flipover technique of the anterior mitral leaflet

We report a new technique for reinforcement of a friable posterior mitral annulus using the anterior leaflet after removing a calcified artificial ring. A 72-year-old woman underwent mitral valve replacement for mitral stenosis and recurrence of regurgitation after mitral valve repair at 53 years of age. She had been on chronic hemodialysis for 20 years. The posterior mitral annulus became highly friable after débridement of the calcified artificial ring. The anterior mitral leaflet was detached from its annulus and transferred to the posterior annulus to cover the defect. The anterior leaflet was anchored to the posterior annulus by valve sutures, and mitral valve replacement was performed successfully. Postoperative ultrasonic cardiography revealed preservation of left ventricular function with no perivalvular leakage.

Ground state configurations of vertically coupled quantum rings

AbstractThe ground states of two vertically coupled quantum rings are studied within the spin density functional theory for systems containing up to 13 electrons. Quantum tunneling effects on the electronic structure of the coupled rings are analyzed. New ground state configurations are found showing the formation of new diatomic artificial ring molecules. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Artificial molecular quantum rings: Spin density functional theory calculations

The ground states of artificial molecules made of two vertically coupled quantum rings are studied within the spin density functional theory for systems containing up to 13 electrons. Quantum tunneling effects on the electronic structure of the coupled rings are analyzed. For small ring radius, our results recover those of coupled quantum dots. For intermediate and large ring radius, new phases are found showing the formation of new diatomic artificial ring molecules. Our results also show that the tunneling induced phase transitions in the coupled rings occur at much smaller tunneling energy as compared to those for coupled quantum dot systems.

How to perform measurements in a hovering animal's wake: physical modelling of the vortex wake of the hawkmoth, Manduca sexta.

The vortex wake structure of the hawkmoth, Manduca sexta, was investigated using a vortex ring generator. Based on existing kinematic and morphological data, a piston and tube apparatus was constructed to produce circular vortex rings with the same size and disc loading as a hovering hawkmoth. Results show that the artificial rings were initially laminar, but developed turbulence owing to azimuthal wave instability. The initial impulse and circulation were accurately estimated for laminar rings using particle image velocimetry; after the transition to turbulence, initial circulation was generally underestimated. The underestimate for turbulent rings can be corrected if the transition time and velocity profile are accurately known, but this correction will not be feasible for experiments on real animals. It is therefore crucial that the circulation and impulse be estimated while the wake vortices are still laminar. The scaling of the ring Reynolds number suggests that flying animals of about the size of hawkmoths may be the largest animals whose wakes stay laminar for long enough to perform such measurements during hovering. Thus, at low advance ratios, they may be the largest animals for which wake circulation and impulse can be accurately measured.

Structural Analysis of Liquid Chalcogen by RMC Modeling with a Dimer Molecule Model

RMC calculations with dimer molecules as a basic unit were performed for liquid selenium and tellurium at several temperatures, and the structure models reproducing the neutron diffraction patterns were obtained. For Se, in order to eliminate the artificial 3-membered rings, a restriction limiting the bond angles was introduced. From the obtained structure model, the covalent bonds were determined and the network structure was analyzed. The local structure parameters, such as bond length, bond angles and coordination number, were also analyzed at each temperature. The distribution of the obtained parameters were reasonable. The branches of chains shown increasing tendency with increasing temperature.

Stability of a ring of connected satellites

The motion of a large number of artificial satellites connected in a ring one after another by tethers of variable length is considered. Every satellite is supposed to have a control system programmed according to some tether tension law as a function of the distance between tethered satellites. The effect of the tension control law on the stability of stationary rotation of this ring is investigated. The final stability condition includes two requirements: 1) the nominal tether tension should be less than a definite limit equal, up to numerical coefficient, to one satellite weight divided by the number of satellites; 2) tether tension should decrease (or remain constant) with the increase of the distance between tethered satellites. In dynamics the artificial rings of this kind are much like their natural prototype—meteor rings. On the other hand, the investigation of the artificial rings contributes to developing an unexpected view upon meteor rings, suggesting a model of an imaginary equivalent string.

A Note on Zeno's Arrow

The paradox, I conjecture, had the following form: (1) Anything that is occupying a space just its own size is at rest. (2) A moving arrow, while it is moving, is moving in the present. (3) But in the present the arrow is occupying a space just its own size. (4) Therefore, in the present the arrow is at rest. (5) Therefore a moving arrow, while it is moving, is at rest. Two items about the reconstruction deserve mention. First, I have interpreted the phrase 'is against what is equal' (xtTo T61L'oov) as 'is occupying a space just its own size'. The Greeks notoriously had difficulty working out a conception of space and the interpretation, I think, preserves the sense of the Greek while sparing us its artificial ring. Second, the phrase, 'in the now' (EV -v viv) is probably Aristotelian.2 But it does, I shall argue, capture a concept crucial to Zeno's argument which has been overlooked by modem commentators: the concept of the present instant. Commentators tend to interpret Zeno as saying that in a moment the arrow occupies a space its own size.3 And yet much of the strength of the paradox and of Aristotle's response depends on the fact that the moment of travel with which Zeno is concerned is the present moment.4