So-called Valve Research Articles

Trapping of light by discontinuities of magnetization in a gyrotropic (meta) material

We show that an interface between two identical metal/dielectric plane-layered ferromagnetic (meta)materials with different directions of magnetization can support electromagnetic surface waves (SWs) of the visible or near-infrared band. We find that such an interface possesses so-called valve action allowing the propagation of SWs only within definite range of angles (including strictly unidirectional propagation), depending on the mutual orientation of magnetizations in the contacted media and filling factor of ferromagnetics in the metamaterial. Furthermore, these SWs can demonstrate unusual properties for conventional surface plasmon-polaritons, namely, a transverse electromagnetic (TEM) structure with zero angular momentum. We also reveal that in a plane-layered metal/dielectric metamaterial the weak optical gyrotropy can be considerably enhanced due to quasi-static LC resonance in this structure.

Algorithms of test diagnostics of valve circuits

Problem. Valve circuits are a special case of electric circuits. The concepts of the electric circuit and the set of its forming elements do not differ from the conventional ones, that is, its elements are ordinary electrical elements and so-called valves - transistors, thyristors. This article explores the ways to solve problems such as checking the status and finding the failing electrical components. The verification task can be considered as a separate case of electric circuit identification. Therefore, the evaluation of the performance of the valve circuits, the compilation of algorithms for their diagnosis is quite an urgent task. Solving this problem will allow more efficient and qualitative use of complex valve circuits, which exist in various electrical systems used in various sectors of the economy and industry. Goal. The goal is analysis and study of basic algorithms for diagnosing electrical circuits of different types. Methodology . The article deals with some algorithms for the diagnosis of valve circuits, namely: the algorithm for the diagnosis of valve circuits in the absence of restrictions on the choice of reaction sensors, the algorithm of diagnosis based on the information criterion, the algorithm of diagnosis by the method of separation. In addition, the use of current sensors for compiling a test diagnosis algorithm is considered. Results. Diagnosis of parameters can be used to detect gradual failures, to predict the state of an object, and to detect sudden failures, including those that cause a change in the structure of the circle: breakage or circuit closure. Originality . Separation of the electric circuit is proposed, which allows to reduce the information capacity of the algorithm and to simplify the analysis of states. Separation of the object of diagnosis allows to reduce the solution of complex multifactor problem to the solution of several simpler ones. In addition, the division of the circle into separate links allows to reduce the number of built-in sensors. Practical value. Diagnosis algorithms using inductive dividers allow maximum depth of defect detection without the use of built-in sensors. In addition to the influence of parallel circles on each other, the split-diagnostics algorithm is reduced for sequential check of the status of the links from the elements included in series, or each element separately. Key words: algorithm; diagnosis; method; valve; valve circle; sensor; test; failure; check; reactions of the working and faulty circle.

Inertia–gravity waves in inertially stable and unstable shear flows

An inertia–gravity wave (IGW) propagating in a vertically sheared, rotating stratified fluid interacts with the pair of inertial levels that surround the critical level. An exact expression for the form of the IGW is derived here in the case of a linear shear and used to examine this interaction in detail. This expression recovers the classical values of the transmission and reflection coefficients $|T|=\text{e}^{-{\rm\pi}{\it\mu}}$ and $|R|=0$, where ${\it\mu}^{2}=J(1+{\it\nu}^{2})-1/4$, $J$ is the Richardson number and ${\it\nu}$ the ratio between the horizontal transverse and along-shear wavenumbers. For large $J$, a WKB analysis provides an interpretation of this result in term of tunnelling: an IGW incident on the lower inertial level becomes evanescent between the inertial levels, returning to an oscillatory behaviour above the upper inertial level. The amplitude of the transmitted wave is directly related to the decay of the evanescent solution between the inertial levels. In the immediate vicinity of the critical level, the evanescent IGW is well represented by the quasi-geostrophic approximation, so that the process can be interpreted as resulting from the coupling between balanced and unbalanced motion. The exact and WKB solutions describe the so-called valve effect, a dependence of the behaviour in the region between the inertial levels on the direction of wave propagation. For $J<1$ this is shown to lead to an amplification of the wave between the inertial levels. Since the flow is inertially unstable for $J<1$, this establishes a correspondence between the inertial-level interaction and the condition for inertial instability.

Gastroesophageal reflux disease and the presence of pepsin in the tears

The nasolacrimal duct in association with the lacrimal puncta, lacrimal canaliculi and lacrimal sac functions to collect and drain the tear film into the nasal cavity at the inferior nasal meatus where a fold of nasal mucosa, the so-called valve of Hasner, prevents mucous from entering the nose. High-resolution computed tomography demonstrated air inside the sac and nasolacrimal duct in approximately 29.3% of healthy patients suggesting that the system is not completely competent and that air and secretions might reach the precorneal film.Gastroesophageal reflux disease may contribute to dacryostenosis and subsequent primary acquired nasolacrimal duct obstruction. However a cause-effect relationship is unclear and only presumptive unless the presence of pepsin in tears can be demonstrated. Gastroesophageal and extra-esophageal reflux could reach the tear film via the nasolacrimal duct in a retrograde fashion and the middle ear via the Eustachian tube. We postulated that the ascending products of gastroesophageal reflux could cause edema of the nasolacrimal duct mucosa, which might progress to fibrosis and chronic inflammation and, ultimately, complete obstruction of the duct with epiphora.The role of reflux in the initial phase of this pathophysiological mechanisms could be demonstrated indirectly by pepsin. By contrast, the development of dacryostenosis blocking the passage of the nasolacrimal duct and thereby preventing pepsin from reaching the lacrimal film failed to explain the influence of gastroesophageal reflux disease with certainty.

The orientation-effect of exchange bias on giant magnetoimpedance in surface crystallized Co66Fe4B15Si15 amorphous ribbons

A phenomenological model to describe the transverse differential susceptibility in the field-annealed CoFeBSi amorphous ribbon is developed. The exchange bias between surface crystalline layer and amorphous bulk is described by means of an exchange bias field. The model allows one to calculate the external field dependence of the transverse differential susceptibility. It is shown that so-called valve at low frequencies and asymmetric two- peak behavior at high frequencies appear in the transverse susceptibility if the orientation of the exchange bias deviates from the ribbon axis. The calculated results are in a qualitative agreement with the magnetoimpedance profiles observed in experiments and allow one to conclude that the exchange interaction between the surface crystalline layer and amorphous bulk is antiferromagnetic coupling.

Trileaflet valve for VAD use with purged sinus.

Clinical applications of ventricle assist devices continue to be problematic due to thromboembolic complications. The problem originates mainly at the valves, which are usually made of an antithrombogenic material, such as cross-linked bovine pericardium. However, wherever the blood flow is stagnant or forms a recirculation region, a thrombus is likely to form. A similar blood flow is found in the space between the housing of the valve and the leaflets, the so-called valve sinus. Consequently, thrombi are often generated in this region. The novel valve design presented in this article avoids the formation of stagnant flow in the valve sinus during systole by a purge flow. This flow is taken from the main flow through the valve and is directed into each sinus region. The effect is achieved by perforation of the valve sinus with a small orifice at the bottom of the sinus. The purge flow effect is investigated with the computational fluid dynamics (CFD) method. The simulation shows that the purge flow effectively increases flow in the valve sinuses.

Les troubles mictionnels persistant après traitement d'une valve de l'urètre postérieur: incidence et sémiologie

Micturition disorders were studied retrospectively in a series of 165 children over a period of 15 years. Among patients without lesions of the upper tract at the time of diagnosis (group A, n = 131), 18(14%) had persistant nocturnal and diurnal enuresis: one urethral stenosis and six vesicoureteric reflux required surgery: three experienced persistent pollakiuria and enuresis. Among patients with upper urinary tract damage at the time of diagnosis (group B, n = 34), seven presented with recurrent urinary tract infection, five with nocturnal and diurnal enuresis and three with urolithiasis. In the long term, only 52% of them had normal renal function and two were successfully transplanted. Micturition disorders following treatment of posterior uretral valves are frequent and usually related to the so-called valve bladder syndrome. Iatrogenic complications and mortality rate have dramatically decreased during the recent years but long-term renal function impairment remains the most critical problem.

Biomechanics of valvular plane displacement of the heart

There has been no consensus concerning the particular movement of the valvular plane of the heart (VPM). As shown in this study involving a mathematical model based upon the momentum equation and experiments on a specially designed artificial heart pump, the VPM not only results from the shortening of the heart, but also from blood flow within the heart and large blood vessels, from the forces caused by the muscle movements, and from the elastic properties of the heart's suspension. The results of the calculations and the experiments confirm the effect of the so-called valve mechanism and its influence on the economic beating action of the heart.

The behavior of magneto-acoustic-gravity waves near the cusp resonance in a lossless, compressible, isothermal, stratified, electrically conducting and uniformly magnetized atmosphere. II: The valve effect

Abstract In the present paper the behavior of (internal) magneto-acoustic-gravity waves near the cusp resonance in a lossless, compressible, isothermal, stratified, electrically conducting atmosphere that is permeated by a uniform, nearly horizontal magnetic field is re-addressed (Kamp, 1989). The previously analyzed linear conversion of long acoustic-gravity waves into short magneto-acoustic waves that carry off the energy from the resonance region along the magnetic field, is re-analyzed with boundary layer techniques that are based on the smallness of the vertical component of the magnetic field. More specifically the existence of the so-called valve effect for the generated magneto-acoustic mode near the critical level is explicitly demonstrated and shown to be governed by two rivalling effects.

An Improved Surgical Technique for the Complicated Hiatal Hernia with Gastroesophageal Reflux

Although so-called valve reconstruction procedures at the gastroesophageal junction provide marked relief for most patients with gastroesophageal reflux and hiatal hernia, there is a recurrence rate of 10 to 15%. Many of the recurrences are in patients with obesity, severe pulmonary disease, or stricture, or in patients who have developed a recurrence from other previous types of surgical therapy. Since the primary cause of failure in hiatal hernia repair is tension on the distal esophagus, which is created as a result of securing an adequate length of intraabdominal esophagus, the Collis gastroplasty, which lengthens the esophagus by construction of a tube of the lesser curvature of the stomach, combined with a Belsey reconstruction of the gastroesophageal angle and dilation in cases of stricture, has been successfully employed over the past three years in patients with factors that predispose to recurrence. This technique provides adequate length without tension, and in more than 39 such patients there has been no evidence of reflux or recurrence of hernia by clinical symptoms or cine esophagogram. No mortality or significant morbidity has been observed.

Verwendung von Metalloxyd-Schichten mit Plasmakontakt zur Energiewandlung

The photovoltaic effect in oxide layers on so-called valve metalls (Al, Ta, Zr, etc.) can be used on principle also for the direct conversion of energy from radioactive particles (α and β) into electrical energy. It can be expected that the resistivity of these oxide layers against radiation damages because of their usually amorphous structure is higher compared with p- n junctions in monocrystalline semiconductors. Since the photovoltaic effect in these oxide layers is not connected with a metallic (or electrolytic) sandwich contacting it is proposed to use an ionized gas as counter electrode, this gas being possibly ionized by radiactive radiation itself. This method was qualitatively investigated by β-irradiation (Tritium) of Ta 2O 5-layers produced by anodizing.

CARPEL MORPHOLOGY IN THE CRUCIFERAE

In the investigation of the floral anatomy of the Cruciferae and some allied families, with the object of determining the fuindamental floral structure of the groups, the writers have obtained evidence which compels them to reopen a subject of long controversy-the nature of the ovary of the Cruciferae. Further, light is also shed upon the recently proposed theory of carpel polymorphism as applied to this family. The structure of the crucifer gynoecium hlas long been a subject of discussion, especially in regard to the number and type of carpels, and the nature of the septum, or false partition. Students of this subject have held several theories as to the nature of the ovary. Of these the chief are, (i) that the pistil consists of two carpels; (2) that there are four carpels, either in one whorl or in two whorls of two each. That the number of carpels is six has also been maintained; and recently as many as IO-20 have been considered to compose the pistil in some genera. The two-carpel theory seems to be commonly held today. Accordiulg to this understanding there are two open carpels fused edge to edge forming the ovary. The fused margins of these carpels bear the placentae, and outgrowths of the placentae divide the really one-celled ovary. The septum is thus false. Those students holding that there are four carpels lhave generally believed that two of these are reduced or aborted. In such cases the ovules are said to be borne on placenital surfaces (of which there are four), placed between the normal and the reduced carpels; and opinions have varied as to the carpel to which the ovules belong, and hence which type of carpel is sterile and which is fertile. A prominent theory, put forth and emphasized by older writers, and recently renewed, and supported with new facts by Miss Saunders (26), is that the so-called valves of the ovary make up the sterile carpels, the fertile carpels being composed of the segments between the valves. The relationship of these two types of carpels can be understood by reference to text figure I. Many supporters of this theory, as well as of the two-carpel theory, have considered the septum, or false partition, to be a secondary placental outgrowth. A few have considered this dissepiment to represent carpellary tissue of the fertile carpels. If the septum is truly carpellary, then it must represent either the venitral part of the carpel itself or a much expanded margin of the carpel. If the dissepiment is false, that is, of placental